Implemented tenant model.

ucalc/BillingWindow.xaml

@@ -17,26 +17,33 @@
         <Frame Name="SideBarFrame"
                Source="Pages/SideBar.xaml"
                Width="240"
-               LoadCompleted="OnSideBarFrameLoadCompleted"/>
+               LoadCompleted="OnSideBarFrameLoadCompleted"
+               Focusable="False" />
 
         <TabControl Name="TabControl"
                     BorderBrush="White">
             <TabItem Visibility="Collapsed">
                 <Frame Source="Pages/LandlordPage.xaml"
-                       LoadCompleted="OnLandlordFrameLoadCompleted"/>
+                       LoadCompleted="OnLandlordFrameLoadCompleted"
+                       Focusable="False" />
             </TabItem>
             <TabItem Visibility="Collapsed">
                 <Frame Source="Pages/HousePage.xaml"
-                       LoadCompleted="OnHouseFrameLoadCompleted"/>
+                       LoadCompleted="OnHouseFrameLoadCompleted"
+                       Focusable="False" />
             </TabItem>
             <TabItem Visibility="Collapsed">
-                <Frame Source="Pages/TenantsPage.xaml"/>
+                <Frame Source="Pages/TenantsPage.xaml"
+                       LoadCompleted="OnTenantsFrameLoadCompleted"
+                       Focusable="False" />
             </TabItem>
             <TabItem Visibility="Collapsed">
-                <Frame Source="Pages/CostsPage.xaml"/>
+                <Frame Source="Pages/CostsPage.xaml"
+                       Focusable="False" />
             </TabItem>
             <TabItem Visibility="Collapsed">
-                <Frame Source="Pages/DetailsPage.xaml"/>
+                <Frame Source="Pages/DetailsPage.xaml"
+                       Focusable="False" />
             </TabItem>
         </TabControl>
     </DockPanel>

ucalc/BillingWindow.xaml.cs

@@ -10,18 +10,16 @@ namespace UCalc
 {
     public partial class BillingWindow
     {
-        public Billing Billing { get; }
-        public BillingModel Model { get; }
+        public Model Model { get; }
 
-        public BillingWindow(Billing savedBilling, Billing billing)
+        public BillingWindow(Billing billing)
         {
-            Billing = billing;
+            Model = new Model(billing);
+
             InitializeComponent();
 
-            Model = new BillingModel(Billing);
-
             Title =
-                $"MietRechner - Abrechnung von {billing.StartDate.ToShortDateString()} - {billing.EndDate.Date.ToShortDateString()}";
+                $"MietRechner - Abrechnung von {billing.StartDate.ToString(Constants.DateFormat)} - {billing.EndDate.Date.ToString(Constants.DateFormat)}";
         }
 
         private void OnClosed(object sender, EventArgs e)
@@ -41,13 +39,21 @@ namespace UCalc
         private void OnLandlordFrameLoadCompleted(object sender, NavigationEventArgs e)
         {
             var page = (LandlordPage) ((Frame) sender).Content;
-            page.Model = Model.LandlordModel;
+            page.Landlord = Model.Root.Landlord;
         }
 
         private void OnHouseFrameLoadCompleted(object sender, NavigationEventArgs e)
         {
             var page = (HousePage) ((Frame) sender).Content;
-            page.Model = Model.HouseModel;
+            page.House = Model.Root.House;
+            page.ParentWindow = this;
+        }
+
+        private void OnTenantsFrameLoadCompleted(object sender, NavigationEventArgs e)
+        {
+            var page = (TenantsPage) ((Frame) sender).Content;
+            page.Tenants = Model.Root.Tenants;
+            page.House = Model.Root.House;
             page.ParentWindow = this;
         }
     }

ucalc/Constants.cs

@@ -11,6 +11,9 @@ namespace UCalc
         public static readonly SolidColorBrush MainColor = Brushes.White;
         public static readonly SolidColorBrush SubMainColor = new SolidColorBrush(Color.FromRgb(0x00, 0x7A, 0xCC));
 
+        public const string DecimalFormat = ".00";
+        public const string DateFormat = "dd.MM.yyyy";
+
         public static readonly ImmutableList<string> SalutationStrs =
             ((Salutation[]) Enum.GetValues(typeof(Salutation))).Select(value => value.AsString()).ToImmutableList();
     }

ucalc/Controls/Converters.cs

@@ -1,19 +1,20 @@
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Windows;
 using System.Windows.Data;
+using UCalc.Models;
 
 namespace UCalc.Controls
 {
     public class ErrorsToVisibilityConverter : IValueConverter
     {
-        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
         {
             return (((ICollection<string>) value)?.Count ?? 0) == 0 ? Visibility.Collapsed : Visibility.Visible;
         }
 
-        public object ConvertBack(object value, Type targetType, object parameter,
-            System.Globalization.CultureInfo culture)
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
         {
             throw new InvalidOperationException();
         }
@@ -23,31 +24,93 @@ namespace UCalc.Controls
     {
         private readonly ErrorsToVisibilityConverter _converter = new ErrorsToVisibilityConverter();
 
-        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
         {
             var result = _converter.Convert(value, targetType, parameter, culture) as Visibility?;
             return result == Visibility.Collapsed ? Visibility.Visible : Visibility.Collapsed;
         }
 
-        public object ConvertBack(object value, Type targetType, object parameter,
-            System.Globalization.CultureInfo culture)
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
         {
             throw new InvalidOperationException();
         }
     }
 
-
-    public class ErrorCountToVisibilityConverter : IValueConverter
+    public class ErrorsToCountConverter : IValueConverter
     {
-        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
         {
-            return (int?) value != 0 ? Visibility.Visible : Visibility.Collapsed;
+            return ((ICollection<string>) value)?.Count ?? 0;
         }
 
-        public object ConvertBack(object value, Type targetType, object parameter,
-            System.Globalization.CultureInfo culture)
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
         {
             throw new InvalidOperationException();
         }
     }
+
+    public class ErrorsToToolTipConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            var errors = (IReadOnlyList<string>) value;
+
+            return (errors?.Count ?? 0) == 0 ? null : string.Join("\n", errors);
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            throw new InvalidOperationException();
+        }
+    }
+
+    public class FlatToRentedConverter : IValueConverter
+    {
+        public TenantProperty Tenant { get; set; }
+
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            return Tenant.RentedFlats.Contains((FlatProperty) value);
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            throw new InvalidOperationException();
+        }
+    }
+
+    public class EmptyMultiPropertyToVisibilityConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            return value?.Equals(0) ?? false ? Visibility.Visible : Visibility.Collapsed;
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            throw new InvalidOperationException();
+        }
+    }
+
+    public class DatePickerTextToDateTimeConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            var dateTime = (DateTime?) value;
+
+            return dateTime == null ? "" : dateTime.Value.ToString(Constants.DateFormat);
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            var str = (string) value;
+
+            if (DateTime.TryParseExact(str, Constants.DateFormat, null, DateTimeStyles.None, out var d))
+            {
+                return d;
+            }
+
+            return null;
+        }
+    }
 }

ucalc/Controls/ErrorCounter.xaml

@@ -7,16 +7,17 @@
              mc:Ignorable="d">
 
     <UserControl.Resources>
-        <local:ErrorCountToVisibilityConverter x:Key="ErrorCountToVisibilityConverter" />
+        <local:ErrorsToVisibilityConverter x:Key="ErrorsToVisibilityConverter" />
+        <local:ErrorsToCountConverter x:Key="ErrorsToCountConverter" />
     </UserControl.Resources>
 
     <Border CornerRadius="3"
             BorderBrush="Red"
             Background="Red"
-            Visibility="{Binding Path=Model.ErrorCount, RelativeSource={RelativeSource AncestorType=local:ErrorCounter}, Converter={StaticResource ErrorCountToVisibilityConverter}}">
+            Visibility="{Binding Path=Property.Errors, RelativeSource={RelativeSource AncestorType=local:ErrorCounter}, Converter={StaticResource ErrorsToVisibilityConverter}}">
 
         <Label
-            Content="{Binding Path=Model.ErrorCount, RelativeSource={RelativeSource AncestorType=local:ErrorCounter}}"
+            Content="{Binding Path=Property.Errors, RelativeSource={RelativeSource AncestorType=local:ErrorCounter}, Converter={StaticResource ErrorsToCountConverter}}"
             Foreground="White" />
 
     </Border>

ucalc/Controls/ErrorCounter.xaml.cs

@@ -5,10 +5,10 @@ namespace UCalc.Controls
 {
     public partial class ErrorCounter
     {
-        public Model Model { get; set; }
+        public Property Property { get; set; }
 
-        public static readonly DependencyProperty ModelProperty = DependencyProperty.Register(
-            "Model", typeof(Model), typeof(ErrorCounter), new PropertyMetadata((Model) null));
+        public static readonly DependencyProperty PropertyProperty = DependencyProperty.Register(
+            "Property", typeof(Property), typeof(ErrorCounter), new PropertyMetadata((Property) null));
 
         public ErrorCounter()
         {

ucalc/Controls/ErrorIcon.xaml

@@ -11,11 +11,12 @@
     <UserControl.Resources>
         <controls:ErrorsToVisibilityConverter x:Key="ErrorsToVisibilityConverter" />
         <controls:ErrorsToInVisibilityConverter x:Key="ErrorsToInVisibilityConverter" />
+        <controls:ErrorsToToolTipConverter x:Key="ErrorsToToolTipConverter" />
     </UserControl.Resources>
     
-    <StackPanel ToolTip="{Binding Path=ErrorsToolTip, RelativeSource={RelativeSource AncestorType=controls:ErrorIcon}}">
+    <StackPanel ToolTip="{Binding Path=Property.Errors, RelativeSource={RelativeSource AncestorType=controls:ErrorIcon}, Converter={StaticResource ErrorsToToolTipConverter}}">
         <Viewbox
-            Visibility="{Binding Path=Errors, RelativeSource={RelativeSource AncestorType=controls:ErrorIcon}, Converter={StaticResource ErrorsToInVisibilityConverter}}"
+            Visibility="{Binding Path=Property.Errors, RelativeSource={RelativeSource AncestorType=controls:ErrorIcon}, Converter={StaticResource ErrorsToInVisibilityConverter}}"
             Stretch="Uniform">
             <Canvas Width="512" Height="512">
                 <Canvas.RenderTransform>
@@ -32,7 +33,7 @@
         </Viewbox>
 
         <Viewbox
-            Visibility="{Binding Path=Errors, RelativeSource={RelativeSource AncestorType=controls:ErrorIcon}, Converter={StaticResource ErrorsToVisibilityConverter}}"
+            Visibility="{Binding Path=Property.Errors, RelativeSource={RelativeSource AncestorType=controls:ErrorIcon}, Converter={StaticResource ErrorsToVisibilityConverter}}"
             Stretch="Uniform">
             <Canvas Width="512" Height="512">
                 <Canvas.RenderTransform>

ucalc/Controls/ErrorIcon.xaml.cs

@@ -1,40 +1,18 @@
-using System.Collections.Generic;
-using System.ComponentModel;
-using System.Runtime.CompilerServices;
-using System.Windows;
-using UCalc.Annotations;
+using System.Windows;
+using UCalc.Models;
 
 namespace UCalc.Controls
 {
-    public partial class ErrorIcon : INotifyPropertyChanged
+    public partial class ErrorIcon
     {
-        public ICollection<string> Errors { get; set; }
+        public Property Property { get; set; }
 
-        public string ErrorsToolTip { get; private set; }
-
-        public static readonly DependencyProperty ErrorsProperty = DependencyProperty.Register(
-            "Errors", typeof(ICollection<string>), typeof(ErrorIcon),
-            new PropertyMetadata(null, OnErrorsChanged));
+        public static readonly DependencyProperty PropertyProperty = DependencyProperty.Register(
+            "Property", typeof(Property), typeof(ErrorIcon), new PropertyMetadata((Property) null));
 
         public ErrorIcon()
         {
             InitializeComponent();
         }
-
-        private static void OnErrorsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
-        {
-            var self = (ErrorIcon) d;
-            var newErrors = (ICollection<string>) e.NewValue;
-            self.ErrorsToolTip = newErrors.Count > 0 ? string.Join("\n", newErrors) : null;
-            self.OnPropertyChanged("ErrorsToolTip");
-        }
-
-        public event PropertyChangedEventHandler PropertyChanged;
-
-        [NotifyPropertyChangedInvocator]
-        private void OnPropertyChanged([CallerMemberName] string propertyName = null)
-        {
-            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
-        }
     }
 }

ucalc/Controls/Helpers.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Media;
@@ -26,5 +27,15 @@ namespace UCalc.Controls
                 path.Fill = brush;
             }
         }
+
+        private static bool IsBetween(this DateTime dt, DateTime start, DateTime end)
+        {
+            return dt >= start && dt <= end;
+        }
+
+        public static bool Intersects(this DateTime start1, DateTime end1, DateTime start2, DateTime end2)
+        {
+            return start1.IsBetween(start2, end2) || start2.IsBetween(start1, end1);
+        }
     }
 }

ucalc/Data/Billing.cs

@@ -167,7 +167,7 @@ namespace UCalc.Data
         public int PersonCount { get; set; }
         public BankAccount BankAccount { get; private set; }
         public DateTime? EntryDate { get; set; }
-        public DateTime? DepatureDate { get; set; }
+        public DateTime? DepartureDate { get; set; }
         public HashSet<Flat> RentedFlats { get; private set; }
         public decimal PaidRent { get; set; }
         public string CustomMessage1 { get; set; }
@@ -185,7 +185,7 @@ namespace UCalc.Data
         {
             return Id.Equals(other.Id) && Salutation == other.Salutation && Name == other.Name &&
                    PersonCount == other.PersonCount && Equals(BankAccount, other.BankAccount) &&
-                   Nullable.Equals(EntryDate, other.EntryDate) && Nullable.Equals(DepatureDate, other.DepatureDate) &&
+                   Nullable.Equals(EntryDate, other.EntryDate) && Nullable.Equals(DepartureDate, other.DepartureDate) &&
                    RentedFlats.SequenceEqual(other.RentedFlats) && PaidRent == other.PaidRent &&
                    CustomMessage1 == other.CustomMessage1 && CustomMessage2 == other.CustomMessage2;
         }
@@ -207,7 +207,7 @@ namespace UCalc.Data
                 PersonCount = PersonCount,
                 BankAccount = BankAccount.Clone(),
                 EntryDate = EntryDate,
-                DepatureDate = DepatureDate,
+                DepartureDate = DepartureDate,
                 RentedFlats = new HashSet<Flat>(RentedFlats.Select(flat => flatMapper[flat])),
                 PaidRent = PaidRent,
                 CustomMessage1 = CustomMessage1,

ucalc/FlatWindow.xaml

@@ -43,12 +43,12 @@
                     <controls:ErrorIcon Margin="12, 0, 0, 0"
                                         DockPanel.Dock="Right"
                                         VerticalAlignment="Center"
-                                        Errors="{Binding Path=Model.Name.Errors, RelativeSource={RelativeSource AncestorType=local:FlatWindow}}" />
+                                        Property="{Binding Path=Flat.Name, RelativeSource={RelativeSource AncestorType=local:FlatWindow}}" />
 
                     <TextBox
                         VerticalAlignment="Center"
                         MinHeight="22"
-                        Text="{Binding Path=Model.Name.Value, RelativeSource={RelativeSource AncestorType=local:FlatWindow}, UpdateSourceTrigger=PropertyChanged}" />
+                        Text="{Binding Path=Flat.Name.Value, RelativeSource={RelativeSource AncestorType=local:FlatWindow}, UpdateSourceTrigger=PropertyChanged}" />
                 </DockPanel>
 
                 <DockPanel Margin="12, 8, 12, 0">
@@ -60,12 +60,12 @@
                     <controls:ErrorIcon Margin="12, 0, 0, 0"
                                         DockPanel.Dock="Right"
                                         VerticalAlignment="Center"
-                                        Errors="{Binding Path=Model.Size.Errors, RelativeSource={RelativeSource AncestorType=local:FlatWindow}}" />
+                                        Property="{Binding Path=Flat.Size, RelativeSource={RelativeSource AncestorType=local:FlatWindow}}" />
 
                     <TextBox
                         VerticalAlignment="Center"
                         MinHeight="22"
-                        Text="{Binding Path=Model.Size.Value, RelativeSource={RelativeSource AncestorType=local:FlatWindow}, UpdateSourceTrigger=PropertyChanged}" />
+                        Text="{Binding Path=Flat.Size.Value, RelativeSource={RelativeSource AncestorType=local:FlatWindow}, UpdateSourceTrigger=PropertyChanged}" />
                 </DockPanel>
             </StackPanel>
         </ScrollViewer>

ucalc/FlatWindow.xaml.cs

@@ -5,11 +5,11 @@ namespace UCalc
 {
     public partial class FlatWindow
     {
-        public FlatModel Model { get; }
+        public FlatProperty Flat { get; }
 
-        public FlatWindow(FlatModel model)
+        public FlatWindow(FlatProperty flat)
         {
-            Model = model;
+            Flat = flat;
             InitializeComponent();
         }
 

ucalc/MainWindow.xaml

@@ -8,6 +8,7 @@
         Title="MietRechner"
         Height="400"
         Width="500"
+        WindowStartupLocation="CenterScreen"
         ResizeMode="CanMinimize">
 
     <Grid>

ucalc/MainWindow.xaml.cs

@@ -22,7 +22,7 @@ namespace UCalc
 
             if (newWindow.ShowDialog() == true)
             {
-                new BillingWindow(newWindow.SavedBilling, newWindow.Billing).Show();
+                new BillingWindow(newWindow.Billing).Show();
                 Hide();
             }
         }
@@ -75,7 +75,7 @@ namespace UCalc
                 var billing = new BillingLoader().Load(path);
                 App.RecentlyOpenedList.Add(new RecentlyOpenedItem(path));
 
-                new BillingWindow(billing, billing.Clone()).Show();
+                new BillingWindow(billing).Show();
                 Hide();
             }
             catch (IOException)

ucalc/Models/AddressModel.cs

@@ -1,39 +0,0 @@
-using UCalc.Data;
-
-namespace UCalc.Models
-{
-    public class AddressModel : Model
-    {
-        private readonly Address _data;
-        public ModelProperty<string> Street { get; }
-        public ModelProperty<string> HouseNumber { get; }
-        public ModelProperty<string> City { get; }
-        public ModelProperty<string> Postcode { get; }
-
-        public AddressModel(Address data)
-        {
-            _data = data;
-
-            Street = Add(new ModelProperty<string>("Straße", _data.Street, ModelPropertyValidators.IsNotEmpty));
-            HouseNumber =
-                Add(new ModelProperty<string>("Hausnummer", _data.HouseNumber, ModelPropertyValidators.IsNotEmpty));
-            City = Add(new ModelProperty<string>("Stadt", _data.City, ModelPropertyValidators.IsNotEmpty));
-            Postcode = Add(new ModelProperty<string>("PLZ", _data.Postcode, ModelPropertyValidators.IsNotEmpty));
-        }
-
-        public override void Apply()
-        {
-            _data.Street = Street.Value;
-            Street.ResetModified();
-
-            _data.HouseNumber = HouseNumber.Value;
-            HouseNumber.ResetModified();
-
-            _data.City = City.Value;
-            City.ResetModified();
-
-            _data.Postcode = Postcode.Value;
-            Postcode.ResetModified();
-        }
-    }
-}

ucalc/Models/AddressProperty.cs

@@ -0,0 +1,20 @@
+using UCalc.Data;
+
+namespace UCalc.Models
+{
+    public class AddressProperty : NestedProperty
+    {
+        public NotEmptyStringProperty Street { get; }
+        public NotEmptyStringProperty HouseNumber { get; }
+        public NotEmptyStringProperty City { get; }
+        public NotEmptyStringProperty Postcode { get; }
+
+        public AddressProperty(Model model, Property parent, Address data) : base(model, parent)
+        {
+            Street = Add(new NotEmptyStringProperty(model, this, "Straße", data.Street));
+            HouseNumber = Add(new NotEmptyStringProperty(model, this, "Hausnummer", data.HouseNumber));
+            City = Add(new NotEmptyStringProperty(model, this, "Stadt", data.City));
+            Postcode = Add(new NotEmptyStringProperty(model, this, "PLZ", data.Postcode));
+        }
+    }
+}

ucalc/Models/BankAccountModel.cs

@@ -1,34 +0,0 @@
-using UCalc.Data;
-
-namespace UCalc.Models
-{
-    public class BankAccountModel : Model
-    {
-        private readonly BankAccount _data;
-        public ModelProperty<string> Iban { get; }
-        public ModelProperty<string> Bic { get; }
-        public ModelProperty<string> BankName { get; }
-
-        public BankAccountModel(BankAccount data)
-        {
-            _data = data;
-
-            Iban = Add(new ModelProperty<string>("IBAN", _data.Iban, ModelPropertyValidators.IsNotEmpty));
-            Bic = Add(new ModelProperty<string>("BIC", _data.Bic, ModelPropertyValidators.IsNotEmpty));
-            BankName = Add(new ModelProperty<string>("Name der Bank", _data.BankName,
-                ModelPropertyValidators.IsNotEmpty));
-        }
-
-        public override void Apply()
-        {
-            _data.Iban = Iban.Value;
-            Iban.ResetModified();
-
-            _data.Bic = Bic.Value;
-            Bic.ResetModified();
-
-            _data.BankName = BankName.Value;
-            BankName.ResetModified();
-        }
-    }
-}

ucalc/Models/BankAccountProperty.cs

@@ -0,0 +1,18 @@
+using UCalc.Data;
+
+namespace UCalc.Models
+{
+    public class BankAccountProperty : NestedProperty
+    {
+        public NotEmptyStringProperty Iban { get; }
+        public NotEmptyStringProperty Bic { get; }
+        public NotEmptyStringProperty BankName { get; }
+
+        public BankAccountProperty(Model model, Property parent, BankAccount data) : base(model, parent)
+        {
+            Iban = Add(new NotEmptyStringProperty(model, this, "IBAN", data.Iban));
+            Bic = Add(new NotEmptyStringProperty(model, this, "BIC", data.Bic));
+            BankName = Add(new NotEmptyStringProperty(model, this, "Name der Bank", data.BankName));
+        }
+    }
+}

ucalc/Models/BillingModel.cs

@@ -1,22 +0,0 @@
-using UCalc.Data;
-
-namespace UCalc.Models
-{
-    public class BillingModel : Model
-    {
-        public LandlordModel LandlordModel { get; }
-        public HouseModel HouseModel { get; }
-
-        public BillingModel(Billing billing)
-        {
-            LandlordModel = new LandlordModel(billing.Landlord);
-            HouseModel = new HouseModel(billing.House);
-        }
-
-        public override void Apply()
-        {
-            LandlordModel.Apply();
-            HouseModel.Apply();
-        }
-    }
-}

ucalc/Models/BillingProperty.cs

@@ -0,0 +1,29 @@
+using System.Collections.Generic;
+using UCalc.Data;
+
+namespace UCalc.Models
+{
+    public class BillingProperty : NestedProperty
+    {
+        public LandlordProperty Landlord { get; }
+        public HouseProperty House { get; }
+        public TenantsProperty Tenants { get; }
+
+
+        // TODO: Costs
+
+        public BillingProperty(Model model, Property parent, Billing data) : base(model, parent)
+        {
+            Landlord = Add(new LandlordProperty(model, this, data.Landlord));
+            House = Add(new HouseProperty(model, this, data.House));
+
+            var flatToProperty = new Dictionary<Flat, FlatProperty>();
+            for (var i = 0; i < data.House.Flats.Count; ++i)
+            {
+                flatToProperty.Add(data.House.Flats[i], House.Flats[i]);
+            }
+
+            Tenants = Add(new TenantsProperty(model, this, data.Tenants, flatToProperty));
+        }
+    }
+}

ucalc/Models/FlatModel.cs

@@ -1,40 +0,0 @@
-using System.Collections.Generic;
-using System.Linq;
-using UCalc.Data;
-
-namespace UCalc.Models
-{
-    public class FlatModel : Model
-    {
-        public Flat Data { get; }
-        public ModelProperty<string> Name { get; }
-        public ModelProperty<string> Size { get; }
-
-        public FlatModel(Flat data, IReadOnlyList<Flat> flats)
-        {
-            Data = data;
-
-            Name = Add(new ModelProperty<string>("Name", Data.Name, (name, value) =>
-            {
-                var error = ModelPropertyValidators.IsNotEmpty(name, value);
-
-                if (error == "" && flats.Any(flat => !ReferenceEquals(flat, Data) && flat.Name == value))
-                {
-                    error = $"{name}: Der Wert \"{value}\" ist nicht eindeutig.";
-                }
-
-                return error;
-            }));
-            Size = Add(new ModelProperty<string>("Größe", Data.Size.ToString(), ModelPropertyValidators.IsNaturalInt));
-        }
-
-        public override void Apply()
-        {
-            Data.Name = Name.Value;
-            Name.ResetModified();
-
-            Data.Size = int.TryParse(Size.Value, out var n) && n > 0 ? n : 0;
-            Size.ResetModified();
-        }
-    }
-}

ucalc/Models/FlatProperty.cs

@@ -0,0 +1,39 @@
+using System.Linq;
+using UCalc.Data;
+
+namespace UCalc.Models
+{
+    public class FlatNameProperty : ValueProperty<string>
+    {
+        public FlatNameProperty(Model model, Property parent, string name, string value) : base(model, parent, name,
+            value)
+        {
+        }
+
+        protected override string ValidateValue()
+        {
+            var error = "";
+            using var validator = Model.BeginValidation();
+
+            if (Model.Root.House.Flats.Any(flat => !ReferenceEquals(this, flat.Name) && flat.Name.Value == Value))
+            {
+                error = $"{Name}: Der Name ist nicht eindeutig.";
+            }
+
+            validator.ValidateRange(Model.Root.House.Flats.Select(flat => flat.Name));
+            return error;
+        }
+    }
+
+    public class FlatProperty : NestedProperty
+    {
+        public FlatNameProperty Name { get; }
+        public NaturalNumberProperty Size { get; }
+
+        public FlatProperty(Model model, Property parent, Flat data) : base(model, parent)
+        {
+            Name = Add(new FlatNameProperty(model, this, "Name", data.Name));
+            Size = Add(new NaturalNumberProperty(model, this, "Größe", data.Size));
+        }
+    }
+}

ucalc/Models/FlatsProperty.cs

@@ -0,0 +1,55 @@
+using System.Collections.Generic;
+using System.Linq;
+using UCalc.Data;
+
+namespace UCalc.Models
+{
+    public class FlatsProperty : MultiProperty<FlatProperty>
+    {
+        public FlatsProperty(Model model, Property parent, IEnumerable<Flat> data) : base(model, parent,
+            "Wohnungen: Geben Sie eine oder mehr Wohnungen an.")
+        {
+            using var validator = Model.BeginValidation();
+
+            foreach (var flat in data)
+            {
+                base.Add(new FlatProperty(Model, this, flat));
+            }
+
+            Modified = false;
+        }
+
+        public void Add()
+        {
+            FlatProperty flat;
+            {
+                using var validator = Model.BeginValidation();
+
+                flat = new FlatProperty(Model, this, new Flat {Name = $"Wohnung {Properties.Count + 1}"});
+                base.Add(flat);
+            }
+
+            {
+                using var validator = Model.BeginValidation();
+                validator.Validate(flat);
+            }
+        }
+
+        public new void Remove(FlatProperty flat)
+        {
+            using var validator = Model.BeginValidation();
+
+            base.Remove(flat);
+
+            // Revalidate flat names and flat lists in tenants and costs
+            validator.ValidateRange(Properties.Select(otherFlat => otherFlat.Name));
+
+            foreach (var tenant in Model.Root.Tenants)
+            {
+                tenant.RentedFlats.Remove(flat);
+            }
+
+            // TODO: Revalidate all flats + revalidate tenant rent lists + costs flat lists
+        }
+    }
+}

ucalc/Models/HouseModel.cs

@@ -1,57 +0,0 @@
-using UCalc.Data;
-
-namespace UCalc.Models
-{
-    public class HouseModel : Model
-    {
-        private readonly House _data;
-        public NestedModelProperty<AddressModel> Address { get; }
-        public MultiModelProperty<FlatModel> Flats { get; }
-
-        public HouseModel(House data)
-        {
-            _data = data;
-
-            Address = Add(new NestedModelProperty<AddressModel>(new AddressModel(_data.Address)));
-            Flats = Add(new MultiModelProperty<FlatModel>());
-
-            foreach (var flat in data.Flats)
-            {
-                Flats.Add(new FlatModel(flat, _data.Flats));
-            }
-        }
-
-        public override void Apply()
-        {
-            Address.Model.Apply();
-
-            foreach (var model in Flats.Models)
-            {
-                model.Apply();
-            }
-        }
-
-        public FlatModel AddFlat()
-        {
-            var flat = new Flat {Name = $"Wohnung {_data.Flats.Count + 1}"};
-            _data.Flats.Add(flat);
-
-            var model = new FlatModel(flat, _data.Flats);
-            Flats.Add(model);
-
-            return model;
-        }
-
-        public void RemoveFlat(FlatModel model)
-        {
-            _data.Flats.Remove(model.Data);
-
-            Flats.Remove(model);
-
-            if (model.Errors.Count > 0)
-            {
-                OnPropertyChanged("Errors");
-            }
-        }
-    }
-}

ucalc/Models/HouseProperty.cs

@@ -0,0 +1,16 @@
+using UCalc.Data;
+
+namespace UCalc.Models
+{
+    public class HouseProperty : NestedProperty
+    {
+        public AddressProperty Address { get; }
+        public FlatsProperty Flats { get; }
+
+        public HouseProperty(Model model, Property parent, House data) : base(model, parent)
+        {
+            Address = Add(new AddressProperty(model, this, data.Address));
+            Flats = Add(new FlatsProperty(model, this, data.Flats));
+        }
+    }
+}

ucalc/Models/LandlordModel.cs

@@ -1,47 +0,0 @@
-using UCalc.Data;
-
-namespace UCalc.Models
-{
-    public class LandlordModel : Model
-    {
-        private readonly Landlord _data;
-        public ModelProperty<int> Salutation { get; }
-        public ModelProperty<string> Name { get; }
-        public ModelProperty<string> MailAddress { get; }
-        public ModelProperty<string> Phone { get; }
-        public NestedModelProperty<AddressModel> Address { get; }
-        public NestedModelProperty<BankAccountModel> BankAccount { get; }
-
-        public LandlordModel(Landlord data)
-        {
-            _data = data;
-
-            Salutation = Add(new ModelProperty<int>("Anrede", (int) _data.Salutation, null));
-            Name = Add(new ModelProperty<string>("Name", _data.Name, ModelPropertyValidators.IsNotEmpty));
-            MailAddress =
-                Add(new ModelProperty<string>("Email Adresse", _data.MailAddress, ModelPropertyValidators.IsNotEmpty));
-            Phone = Add(new ModelProperty<string>("Telefonnummer", _data.Phone, ModelPropertyValidators.IsNotEmpty));
-            Address = Add(new NestedModelProperty<AddressModel>(new AddressModel(_data.Address)));
-            BankAccount = Add(new NestedModelProperty<BankAccountModel>(new BankAccountModel(_data.BankAccount)));
-        }
-
-        public override void Apply()
-        {
-            _data.Salutation = (Salutation) Salutation.Value;
-            Salutation.ResetModified();
-
-            _data.Name = Name.Value;
-            Name.ResetModified();
-
-            _data.MailAddress = MailAddress.Value;
-            MailAddress.ResetModified();
-
-            _data.Phone = Phone.Value;
-            Phone.ResetModified();
-
-            Address.Model.Apply();
-
-            BankAccount.Model.Apply();
-        }
-    }
-}

ucalc/Models/LandlordProperty.cs

@@ -0,0 +1,24 @@
+using UCalc.Data;
+
+namespace UCalc.Models
+{
+    public class LandlordProperty : NestedProperty
+    {
+        public SalutationProperty Salutation { get; }
+        public NotEmptyStringProperty Name { get; }
+        public NotEmptyStringProperty MailAddress { get; }
+        public NotEmptyStringProperty Phone { get; }
+        public AddressProperty Address { get; }
+        public BankAccountProperty BankAccount { get; }
+
+        public LandlordProperty(Model model, Property parent, Landlord data) : base(model, parent)
+        {
+            Salutation = Add(new SalutationProperty(model, this, "Anrede", data.Salutation));
+            Name = Add(new NotEmptyStringProperty(model, this, "Name", data.Name));
+            MailAddress = Add(new NotEmptyStringProperty(model, this, "Email Adresse", data.MailAddress));
+            Phone = Add(new NotEmptyStringProperty(model, this, "Telefonnummer", data.Phone));
+            Address = Add(new AddressProperty(model, this, data.Address));
+            BankAccount = Add(new BankAccountProperty(model, this, data.BankAccount));
+        }
+    }
+}

ucalc/Models/Model.cs

@@ -1,234 +1,152 @@
 using System;
 using System.Collections.Generic;
-using System.Collections.ObjectModel;
 using System.ComponentModel;
-using System.Linq;
 using System.Runtime.CompilerServices;
 using UCalc.Annotations;
+using UCalc.Data;
 
 namespace UCalc.Models
 {
-    public abstract class ModelBaseProperty : INotifyPropertyChanged
+    public class Model : INotifyPropertyChanged
     {
-        protected static readonly List<string> EmptyList = new List<string>();
-        public abstract IReadOnlyCollection<string> Errors { get; }
-        public abstract bool Modified { get; }
+        public class Validator : IDisposable
+        {
+            private readonly Model _model;
+            private int _counter;
+            private readonly HashSet<Property> _validated;
+            private readonly HashSet<Tuple<Property, string>> _notifications;
 
-        protected void OnChildPropertyChanged(object sender, PropertyChangedEventArgs args)
+            public Validator(Model model)
             {
-            if (args.PropertyName == "Errors" || args.PropertyName == "Modified")
+                _model = model;
+                _validated = new HashSet<Property>();
+                _notifications = new HashSet<Tuple<Property, string>>();
+            }
+
+            public void Notify(Property property, string propertyName)
             {
-                OnPropertyChanged(args.PropertyName);
+                _notifications.Add(new Tuple<Property, string>(property, propertyName));
+
+                if (property != null)
+                {
+                    property = property.Parent;
+
+                    while (property != null)
+                    {
+                        _notifications.Add(new Tuple<Property, string>(property, propertyName));
+                        property = property.Parent;
+                    }
+
+                    _notifications.Add(new Tuple<Property, string>(null, propertyName));
                 }
             }
 
-        public event PropertyChangedEventHandler PropertyChanged;
-
-        [NotifyPropertyChangedInvocator]
-        protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
+            public void Validate(Property property)
             {
-            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
-        }
-    }
-
-    public class NestedModelProperty<T> : ModelBaseProperty where T : Model
-    {
-        public T Model { get; }
-
-        public NestedModelProperty(T model)
-        {
-            Model = model;
-
-            Model.PropertyChanged += OnChildPropertyChanged;
-        }
-
-        public override IReadOnlyCollection<string> Errors => Model.Errors;
-
-        public override bool Modified => Model.Modified;
-    }
-
-    public class MultiModelProperty<T> : ModelBaseProperty where T : Model
-    {
-        private readonly ObservableCollection<T> _models;
-
-        public MultiModelProperty()
-        {
-            _models = new ObservableCollection<T>();
-        }
-
-        public void Add(T model)
-        {
-            _models.Add(model);
-
-            model.PropertyChanged += OnChildPropertyChanged;
-
-            if (model.Errors.Count > 0)
-            {
-                OnPropertyChanged("Errors");
-            }
-        }
-
-        public void Remove(T model)
-        {
-            model.PropertyChanged -= OnChildPropertyChanged;
-
-            _models.Remove(model);
-
-            if (model.Errors.Count > 0)
-            {
-                OnPropertyChanged("Errors");
-            }
-        }
-
-        public IReadOnlyList<T> Models => _models;
-
-        public override IReadOnlyCollection<string> Errors
-        {
-            get
-            {
-                var errors = new List<string>();
-
-                foreach (var model in _models)
-                {
-                    errors.AddRange(model.Errors);
-                }
-
-                return errors;
-            }
-        }
-
-        public override bool Modified => _models.Select(model => model.Modified).Any();
-    }
-
-    public class ModelProperty<T> : ModelBaseProperty
-    {
-        public string Name { get; }
-        private T _value;
-        private readonly List<string> _errors;
-        private readonly Func<string, T, string> _validate;
-        private bool _modified;
-
-        public T Value
-        {
-            get => _value;
-            set
-            {
-                if (_value.Equals(value))
+                if (property == null)
                 {
                     return;
                 }
 
-                var oldError = _errors[0];
-                _errors[0] = _validate?.Invoke(Name, value) ?? "";
-
-                if (oldError != _errors[0])
+                if (_validated.Add(property))
                 {
-                    OnPropertyChanged("Errors");
-                }
-
-                if (!_modified)
-                {
-                    OnPropertyChanged("Modified");
-                }
-
-                _modified = true;
-                _value = value;
-
-                OnPropertyChanged("Value");
+                    property.Validate();
                 }
             }
 
-        public ModelProperty(string name, T value, Func<string, T, string> validate)
+            public void ValidateRange(IEnumerable<Property> properties)
             {
-            Name = name;
-            _value = value;
-            _errors = new List<string> {validate?.Invoke(Name, _value) ?? ""};
-            _validate = validate;
-            _modified = false;
-        }
-
-        public override IReadOnlyCollection<string> Errors => _errors[0] != "" ? _errors : EmptyList;
-
-        public override bool Modified => _modified;
-
-        public void ResetModified()
+                foreach (var property in properties)
                 {
-            _modified = false;
+                    Validate(property);
                 }
             }
 
-    public static class ModelPropertyValidators
+            public void IncValidationCounter()
             {
-        public static string IsNotEmpty(string name, string data)
-        {
-            return string.IsNullOrEmpty(data) ? $"{name}: Geben Sie einen Wert ein." : "";
+                ++_counter;
             }
 
-        public static string IsNaturalInt(string name, string data)
+            public void Dispose()
             {
-            return !int.TryParse(data, out var n) || n <= 0
-                ? $"{name}: Der eingegebene Wert ist keine gültige positive Zahl > 0."
-                : "";
+                --_counter;
+
+                if (_counter == 0)
+                {
+                    _validated.Clear();
+
+                    var sortedNotifications = new List<Tuple<Property, string>>(_notifications);
+                    sortedNotifications.Sort((x, y) =>
+                    {
+                        var (prop1, propName1) = x;
+                        var (prop2, propName2) = y;
+
+                        if (prop1 == null)
+                        {
+                            return prop2 == null ? string.CompareOrdinal(propName1, propName2) : 1;
+                        }
+
+                        if (prop2 == null)
+                        {
+                            return -1;
+                        }
+
+                        if (ReferenceEquals(prop1, prop2))
+                        {
+                            return string.CompareOrdinal(propName1, propName2);
+                        }
+
+                        if (prop1.IsParentOf(prop2))
+                        {
+                            return 1;
+                        }
+
+                        if (prop2.IsParentOf(prop1))
+                        {
+                            return -1;
+                        }
+
+                        return 0;
+                    });
+
+                    foreach (var (property, propertyName) in sortedNotifications)
+                    {
+                        if (property == null)
+                        {
+                            _model.OnPropertyChanged(propertyName);
+                        }
+                        else
+                        {
+                            property.OnPropertyChanged(propertyName);
                         }
                     }
 
-    public abstract class Model : INotifyPropertyChanged
-    {
-        private readonly List<ModelBaseProperty> _properties;
-
-        protected Model()
-        {
-            _properties = new List<ModelBaseProperty>();
-
-            PropertyChanged += (sender, args) =>
-            {
-                if (args.PropertyName == "Errors")
-                {
-                    OnPropertyChanged("ErrorCount");
+                    _notifications.Clear();
                 }
-            };
-        }
-
-        protected T Add<T>(T property) where T : ModelBaseProperty
-        {
-            _properties.Add(property);
-
-            property.PropertyChanged += (sender, args) =>
-            {
-                if (args.PropertyName == "Errors" || args.PropertyName == "Modified")
-                {
-                    OnPropertyChanged(args.PropertyName);
-                }
-            };
-
-            return property;
-        }
-
-        public bool Modified => _properties.Select(property => property.Modified).Any();
-
-        public IReadOnlyCollection<string> Errors
-        {
-            get
-            {
-                var errors = new List<string>();
-
-                foreach (var property in _properties)
-                {
-                    errors.AddRange(property.Errors);
-                }
-
-                return errors;
             }
         }
 
-        public int ErrorCount => Errors.Count;
+        private readonly Validator _validator;
+        public BillingProperty Root { get; }
 
-        public abstract void Apply();
+        public Model(Billing billing)
+        {
+            _validator = new Validator(this);
+
+            using var validator = BeginValidation();
+            Root = new BillingProperty(this, null, billing);
+        }
+
+        public Validator BeginValidation()
+        {
+            _validator.IncValidationCounter();
+            return _validator;
+        }
 
         public event PropertyChangedEventHandler PropertyChanged;
 
         [NotifyPropertyChangedInvocator]
-        protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
+        private void OnPropertyChanged([CallerMemberName] string propertyName = null)
         {
             PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
         }

ucalc/Models/Properties.cs

@@ -0,0 +1,326 @@
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using System.ComponentModel;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using UCalc.Annotations;
+
+namespace UCalc.Models
+{
+    public abstract class Property : INotifyPropertyChanged
+    {
+        protected static readonly IReadOnlyList<string> EmptyList = new List<string>();
+
+        protected readonly Model Model;
+        public Property Parent { get; }
+
+        public abstract IReadOnlyList<string> Errors { get; }
+
+        private bool _modified;
+
+        public bool Modified
+        {
+            get => _modified;
+            protected set
+            {
+                if (_modified == value)
+                {
+                    return;
+                }
+
+                _modified = value;
+
+                using var validator = Model.BeginValidation();
+                validator.Notify(this, "Modified");
+            }
+        }
+
+        protected Property(Model model, Property parent)
+        {
+            Model = model;
+            Parent = parent;
+        }
+
+        public abstract void Validate();
+
+        public event PropertyChangedEventHandler PropertyChanged;
+
+        [NotifyPropertyChangedInvocator]
+        public virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
+        {
+            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+        }
+
+        public bool IsParentOf(Property property)
+        {
+            while (property != null)
+            {
+                if (ReferenceEquals(this, property))
+                {
+                    return true;
+                }
+
+                property = property.Parent;
+            }
+
+            return false;
+        }
+    }
+
+    public abstract class ValueProperty<T> : Property
+    {
+        protected string Name;
+        private T _value;
+        private readonly List<string> _errors;
+
+        public T Value
+        {
+            get => _value;
+            set
+            {
+                if (_value.Equals(value))
+                {
+                    return;
+                }
+
+                _value = value;
+                OnPropertyChanged();
+
+                using var validator = Model.BeginValidation();
+                Modified = true;
+                validator.Validate(this);
+            }
+        }
+
+        protected ValueProperty(Model model, Property parent, string name, T value) : base(model, parent)
+        {
+            Name = name;
+            _value = value;
+            _errors = new List<string> {""};
+
+            using var validator = Model.BeginValidation();
+            validator.Validate(this);
+        }
+
+        public override IReadOnlyList<string> Errors => _errors[0] != "" ? _errors : EmptyList;
+
+        public sealed override void Validate()
+        {
+            var oldError = _errors[0];
+            _errors[0] = ValidateValue();
+
+            if (oldError != _errors[0])
+            {
+                using var validator = Model.BeginValidation();
+                validator.Notify(this, "Errors");
+            }
+        }
+
+        protected abstract string ValidateValue();
+    }
+
+    public class AlwaysValidProperty<T> : ValueProperty<T>
+    {
+        public AlwaysValidProperty(Model model, Property parent, string name, T value) : base(model, parent,
+            name, value)
+        {
+        }
+
+        protected override string ValidateValue()
+        {
+            return "";
+        }
+    }
+
+    public class NotEmptyStringProperty : ValueProperty<string>
+    {
+        public NotEmptyStringProperty(Model model, Property parent, string name, string value) : base(model, parent,
+            name, value)
+        {
+        }
+
+        protected override string ValidateValue()
+        {
+            return string.IsNullOrEmpty(Value) ? $"{Name}: Geben Sie einen Wert ein." : "";
+        }
+    }
+
+    public class NaturalNumberProperty : ValueProperty<string>
+    {
+        public NaturalNumberProperty(Model model, Property parent, string name, int value) : base(model, parent, name,
+            value.ToString())
+        {
+        }
+
+        protected override string ValidateValue()
+        {
+            return !int.TryParse(Value, out var n) || n <= 0
+                ? $"{Name}: Der eingegebene Wert ist keine gültige Zahl > 0."
+                : "";
+        }
+    }
+
+    public class PositiveDecimalProperty : ValueProperty<string>
+    {
+        public PositiveDecimalProperty(Model model, Property parent, string name, decimal value) : base(model, parent,
+            name,
+            value.ToString(Constants.DecimalFormat))
+        {
+        }
+
+        protected override string ValidateValue()
+        {
+            return !decimal.TryParse(Value, out var n) || n < 0
+                ? $"{Name}: Der eingegebene Wert ist kein gültiger Betrag."
+                : "";
+        }
+    }
+
+    public abstract class NestedProperty : Property
+    {
+        private readonly List<Property> _properties;
+        private readonly List<string> _errors;
+        public override IReadOnlyList<string> Errors => _errors;
+
+        protected NestedProperty(Model model, Property parent) : base(model, parent)
+        {
+            _properties = new List<Property>();
+            _errors = new List<string>();
+        }
+
+        protected T Add<T>(T property) where T : Property
+        {
+            _properties.Add(property);
+            return property;
+        }
+
+        public override void Validate()
+        {
+            using var validator = Model.BeginValidation();
+            validator.ValidateRange(_properties);
+        }
+
+        public override void OnPropertyChanged(string propertyName = null)
+        {
+            switch (propertyName)
+            {
+                case "Errors":
+                    _errors.Clear();
+
+                    foreach (var property in _properties)
+                    {
+                        _errors.AddRange(property.Errors);
+                    }
+
+                    break;
+                case "Modified":
+                    Modified = _properties.Any(property => property.Modified);
+                    break;
+            }
+
+            base.OnPropertyChanged(propertyName);
+        }
+    }
+
+    public abstract class MultiProperty<T> : Property, IReadOnlyList<T>, INotifyCollectionChanged where T : Property
+    {
+        private readonly string _errorOnEmpty;
+        private readonly List<T> _properties;
+        protected IReadOnlyList<T> Properties => _properties;
+        private readonly List<string> _errors;
+        public override IReadOnlyList<string> Errors => _errors;
+
+        protected MultiProperty(Model model, Property parent, string errorOnEmpty = null) : base(model, parent)
+        {
+            _errorOnEmpty = errorOnEmpty;
+            _properties = new List<T>();
+            _errors = new List<string>();
+
+            OnPropertyChanged("Errors");
+        }
+
+        protected void Add(T property)
+        {
+            _properties.Add(property);
+
+            using var validator = Model.BeginValidation();
+            validator.Notify(this, "Errors");
+            Modified = true;
+
+            OnPropertyChanged("Count");
+
+            CollectionChanged?.Invoke(this,
+                new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, property,
+                    _properties.Count - 1));
+        }
+
+        protected void Remove(T property)
+        {
+            var index = _properties.IndexOf(property);
+            _properties.RemoveAt(index);
+
+            using var validator = Model.BeginValidation();
+            validator.Notify(this, "Errors");
+            Modified = true;
+
+            OnPropertyChanged("Count");
+
+            CollectionChanged?.Invoke(this,
+                new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, property, index));
+        }
+
+        public override void Validate()
+        {
+            using var validator = Model.BeginValidation();
+            validator.ValidateRange(_properties);
+        }
+
+        public sealed override void OnPropertyChanged(string propertyName = null)
+        {
+            switch (propertyName)
+            {
+                case "Errors":
+                    _errors.Clear();
+
+                    if (_properties.Count == 0)
+                    {
+                        if (!string.IsNullOrEmpty(_errorOnEmpty))
+                        {
+                            _errors.Add(_errorOnEmpty);
+                        }
+                    }
+                    else
+                    {
+                        foreach (var property in _properties)
+                        {
+                            _errors.AddRange(property.Errors);
+                        }
+                    }
+
+                    break;
+                case "Modified":
+                    Modified = Modified || _properties.Any(property => property.Modified);
+                    break;
+            }
+
+            base.OnPropertyChanged(propertyName);
+        }
+
+        public IEnumerator<T> GetEnumerator()
+        {
+            return _properties.GetEnumerator();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+
+        public int Count => _properties.Count;
+
+        public T this[int index] => _properties[index];
+
+        public event NotifyCollectionChangedEventHandler CollectionChanged;
+    }
+}

ucalc/Models/SalutationProperty.cs

@@ -0,0 +1,12 @@
+using UCalc.Data;
+
+namespace UCalc.Models
+{
+    public class SalutationProperty : AlwaysValidProperty<int>
+    {
+        public SalutationProperty(Model model, Property parent, string name, Salutation value) : base(model, parent,
+            name, (int) value)
+        {
+        }
+    }
+}

ucalc/Models/TenantProperty.cs

@@ -0,0 +1,203 @@
+using System;
+using System.Collections.Generic;
+using UCalc.Controls;
+using UCalc.Data;
+
+namespace UCalc.Models
+{
+    public class EntryDateProperty : ValueProperty<DateTime?>
+    {
+        public EntryDateProperty(Model model, Property parent, string name, DateTime? value) : base(model, parent, name,
+            value)
+        {
+        }
+
+        protected override string ValidateValue()
+        {
+            using var validator = Model.BeginValidation();
+
+            validator.Validate(((TenantProperty) Parent).DepartureDate);
+
+            return "";
+        }
+    }
+
+    public class DepatureDateProperty : ValueProperty<DateTime?>
+    {
+        public DepatureDateProperty(Model model, Property parent, string name, DateTime? value) : base(model, parent,
+            name, value)
+        {
+        }
+
+        protected override string ValidateValue()
+        {
+            if (Value != null)
+            {
+                var entryDate = ((TenantProperty) Parent).EntryDate.Value;
+
+                if (entryDate != null && entryDate > Value)
+                {
+                    return $"{Name}: Das Datum liegt vor dem Einzug.";
+                }
+            }
+
+            using var validator = Model.BeginValidation();
+            validator.Validate(((TenantProperty) Parent).RentedFlats);
+
+            return "";
+        }
+    }
+
+    public class RentedFlatsProperty : Property
+    {
+        private const string NoFlatsError = "Gemietete Wohnungen: Es wurde keine Wohnung zugewiesen.";
+        private readonly HashSet<FlatProperty> _flatProperties;
+        private readonly List<string> _errors;
+
+        public RentedFlatsProperty(Model model, Property parent, IEnumerable<Flat> data,
+            IReadOnlyDictionary<Flat, FlatProperty> flatToProperty = null) : base(model, parent)
+        {
+            _flatProperties = new HashSet<FlatProperty>();
+            _errors = new List<string>();
+
+            foreach (var flat in data)
+            {
+                _flatProperties.Add(flatToProperty?[flat] ?? throw new InvalidOperationException());
+            }
+
+            Validate();
+        }
+
+        public override IReadOnlyList<string> Errors => _errors;
+
+        public void Add(FlatProperty flat)
+        {
+            if (!_flatProperties.Add(flat))
+            {
+                return;
+            }
+
+            using var validator = Model.BeginValidation();
+            validator.Validate(this);
+            Modified = true;
+        }
+
+        public void Remove(FlatProperty flat)
+        {
+            if (!_flatProperties.Remove(flat))
+            {
+                return;
+            }
+
+            using var validator = Model.BeginValidation();
+            validator.Validate(this);
+            Modified = true;
+        }
+
+        public bool Contains(FlatProperty flat)
+        {
+            return _flatProperties.Contains(flat);
+        }
+
+        public sealed override void Validate()
+        {
+            _errors.Clear();
+
+            if (_flatProperties.Count == 0)
+            {
+                _errors.Add(NoFlatsError);
+                return;
+            }
+
+            var entryDate = ((TenantProperty) Parent).EntryDate.Value;
+            var departureDate = ((TenantProperty) Parent).DepartureDate.Value;
+
+            foreach (var flatProperty in _flatProperties)
+            {
+                foreach (var tenant in Model.Root.Tenants)
+                {
+                    if (ReferenceEquals(this, tenant.RentedFlats))
+                    {
+                        continue;
+                    }
+
+                    if (tenant.RentedFlats.IsRented(flatProperty, entryDate, departureDate))
+                    {
+                        var error = $"Gemietete Wohnungen: Die Wohnung \"{flatProperty.Name.Value}\" ist bereits ";
+
+                        if (entryDate != null)
+                        {
+                            if (departureDate != null)
+                            {
+                                _errors.Add(
+                                    $"von {entryDate.Value.ToString(Constants.DateFormat)} - {departureDate.Value.ToString(Constants.DateFormat)} ");
+                            }
+                            else
+                            {
+                                _errors.Add($"seit dem {entryDate.Value.ToString(Constants.DateFormat)} ");
+                            }
+                        }
+                        else if (departureDate != null)
+                        {
+                            _errors.Add($"bis zum {departureDate.Value.ToString(Constants.DateFormat)} ");
+                        }
+
+                        error += "an einen anderen Mieter vermietet.";
+                        _errors.Add(error);
+                        break;
+                    }
+                }
+            }
+
+            using var validator = Model.BeginValidation();
+            validator.Notify(this, "Errors");
+
+            validator.ValidateRange(Model.Root.Tenants);
+        }
+
+        private bool IsRented(FlatProperty flat, DateTime? start, DateTime? end)
+        {
+            if (!_flatProperties.Contains(flat))
+            {
+                return false;
+            }
+
+            var thisStart = ((TenantProperty) Parent).EntryDate.Value ?? DateTime.MinValue;
+            var thisEnd = ((TenantProperty) Parent).DepartureDate.Value ?? DateTime.MaxValue;
+
+            var otherStart = start ?? DateTime.MinValue;
+            var otherEnd = end ?? DateTime.MinValue;
+
+            return thisStart.Intersects(thisEnd, otherStart, otherEnd);
+        }
+    }
+
+    public class TenantProperty : NestedProperty
+    {
+        public SalutationProperty Salutation { get; }
+        public NotEmptyStringProperty Name { get; }
+        public NaturalNumberProperty PersonCount { get; }
+        public BankAccountProperty BankAccount { get; }
+        public EntryDateProperty EntryDate { get; }
+        public DepatureDateProperty DepartureDate { get; }
+        public RentedFlatsProperty RentedFlats { get; }
+        public PositiveDecimalProperty PaidRent { get; }
+        public AlwaysValidProperty<string> CustomMessage1 { get; }
+        public AlwaysValidProperty<string> CustomMessage2 { get; }
+
+        public TenantProperty(Model model, Property parent, Tenant data,
+            IReadOnlyDictionary<Flat, FlatProperty> flatToProperty = null) : base(model, parent)
+        {
+            Salutation = Add(new SalutationProperty(model, this, "Anrede", data.Salutation));
+            Name = Add(new NotEmptyStringProperty(model, this, "Name", data.Name));
+            PersonCount = Add(new NaturalNumberProperty(model, this, "Personenanzahl", data.PersonCount));
+            BankAccount = Add(new BankAccountProperty(model, this, data.BankAccount));
+            EntryDate = Add(new EntryDateProperty(model, this, "Einzugsdatum", data.EntryDate));
+            DepartureDate = Add(new DepatureDateProperty(model, this, "Auszugsdatum", data.DepartureDate));
+            RentedFlats = Add(new RentedFlatsProperty(model, this, data.RentedFlats, flatToProperty));
+            PaidRent = Add(new PositiveDecimalProperty(model, this, "Bereits gezahlt", data.PaidRent));
+            CustomMessage1 = Add(new AlwaysValidProperty<string>(model, this, "Nachricht 1", data.CustomMessage1));
+            CustomMessage2 = Add(new AlwaysValidProperty<string>(model, this, "Nachricht 2", data.CustomMessage2));
+        }
+    }
+}

ucalc/Models/TenantsProperty.cs

@@ -0,0 +1,39 @@
+using System.Collections.Generic;
+using System.Linq;
+using UCalc.Data;
+
+namespace UCalc.Models
+{
+    public class TenantsProperty : MultiProperty<TenantProperty>
+    {
+        public TenantsProperty(Model model, Property parent, IEnumerable<Tenant> data,
+            IReadOnlyDictionary<Flat, FlatProperty> flatToProperty = null) : base(model, parent,
+            "Mieter: Geben Sie einen oder mehr Mieter an.")
+        {
+            using var validator = Model.BeginValidation();
+
+            foreach (var tenant in data)
+            {
+                base.Add(new TenantProperty(Model, this, tenant, flatToProperty));
+            }
+
+            Modified = false;
+        }
+
+        public void Add()
+        {
+            using var validator = Model.BeginValidation();
+
+            base.Add(new TenantProperty(Model, this, new Tenant()));
+        }
+
+        public new void Remove(TenantProperty tenant)
+        {
+            using var validator = Model.BeginValidation();
+
+            base.Remove(tenant);
+
+            validator.ValidateRange(Properties.Select(otherTenant => otherTenant.RentedFlats));
+        }
+    }
+}

ucalc/NewWindow.xaml.cs

@@ -71,7 +71,7 @@ namespace UCalc
                     return;
                 }
 
-                // Remove depatured renters and costs that were only paid once
+                // Remove departured renters and costs that were only paid once
                 string summary = "";
                 billing.StartDate = (DateTime) StartCalendar.SelectedDate;
                 billing.EndDate = (DateTime) EndCalendar.SelectedDate;

ucalc/Pages/HousePage.xaml

@@ -8,6 +8,10 @@
       xmlns:controls="clr-namespace:UCalc.Controls"
       mc:Ignorable="d">
 
+    <Page.Resources>
+        <controls:EmptyMultiPropertyToVisibilityConverter x:Key="EmptyMultiPropertyToVisibilityConverter" />
+    </Page.Resources>
+
     <ScrollViewer HorizontalScrollBarVisibility="Disabled"
                   VerticalScrollBarVisibility="Auto">
         <StackPanel>
@@ -22,12 +26,12 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.Address.Model.Street.Errors, RelativeSource={RelativeSource AncestorType=pages:HousePage}}" />
+                                    Property="{Binding Path=House.Address.Street, RelativeSource={RelativeSource AncestorType=pages:HousePage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.Address.Model.Street.Value, RelativeSource={RelativeSource AncestorType=pages:HousePage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=House.Address.Street.Value, RelativeSource={RelativeSource AncestorType=pages:HousePage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
             <DockPanel Margin="12, 8, 12, 0">
@@ -39,12 +43,12 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.Address.Model.HouseNumber.Errors, RelativeSource={RelativeSource AncestorType=pages:HousePage}}" />
+                                    Property="{Binding Path=House.Address.HouseNumber, RelativeSource={RelativeSource AncestorType=pages:HousePage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.Address.Model.HouseNumber.Value, RelativeSource={RelativeSource AncestorType=pages:HousePage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=House.Address.HouseNumber.Value, RelativeSource={RelativeSource AncestorType=pages:HousePage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
             <DockPanel Margin="12, 8, 12, 0">
@@ -56,12 +60,12 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.Address.Model.City.Errors, RelativeSource={RelativeSource AncestorType=pages:HousePage}}" />
+                                    Property="{Binding Path=House.Address.City, RelativeSource={RelativeSource AncestorType=pages:HousePage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.Address.Model.City.Value, RelativeSource={RelativeSource AncestorType=pages:HousePage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=House.Address.City.Value, RelativeSource={RelativeSource AncestorType=pages:HousePage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
             <DockPanel Margin="12, 8, 12, 0">
@@ -73,18 +77,25 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.Address.Model.Postcode.Errors, RelativeSource={RelativeSource AncestorType=pages:HousePage}}" />
+                                    Property="{Binding Path=House.Address.Postcode, RelativeSource={RelativeSource AncestorType=pages:HousePage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.Address.Model.Postcode.Value, RelativeSource={RelativeSource AncestorType=pages:HousePage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=House.Address.Postcode.Value, RelativeSource={RelativeSource AncestorType=pages:HousePage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
             <controls:SectionHeader Header="Wohnungen"
                                     Margin="0, 12, 0, 0" />
 
-            <controls:HighlightButton Margin="12, 0, 12, 8"
+            <DockPanel Margin="0, 0, 0, 8">
+                <controls:ErrorIcon Margin="0, 0, 12, 0"
+                                    DockPanel.Dock="Right"
+                                    VerticalAlignment="Center"
+                                    Property="{Binding Path=House.Flats, RelativeSource={RelativeSource AncestorType=pages:HousePage}}"
+                                    Visibility="{Binding Path=House.Flats.Count, RelativeSource={RelativeSource AncestorType=pages:HousePage}, Converter={StaticResource EmptyMultiPropertyToVisibilityConverter}}" />
+
+                <controls:HighlightButton Margin="12, 0, 12, 0"
                                           HighlightForeground="{x:Static local:Constants.SubMainColor}"
                                           HighlightBackground="{x:Static local:Constants.MainColor}"
                                           Click="OnAddFlatClick">
@@ -109,9 +120,10 @@
                     <Label Content="Wohnung hinzufügen"
                            Margin="0, 12, 12, 12" />
                 </controls:HighlightButton>
+            </DockPanel>
 
             <ItemsControl
-                ItemsSource="{Binding Path=Model.Flats.Models, RelativeSource={RelativeSource AncestorType=pages:HousePage}}"
+                ItemsSource="{Binding Path=House.Flats, RelativeSource={RelativeSource AncestorType=pages:HousePage}}"
                 Margin="12, 0, 12, 12">
                 <ItemsControl.ItemTemplate>
                     <DataTemplate>
@@ -143,7 +155,7 @@
                                                       HighlightBackground="{x:Static local:Constants.MainColor}"
                                                       Click="OnFlatEditClick">
 
-                                <controls:ErrorIcon Errors="{Binding Errors}"
+                                <controls:ErrorIcon Property="{Binding .}"
                                                     DockPanel.Dock="Left"
                                                     Margin="12, 12, 8, 12" />
 

ucalc/Pages/HousePage.xaml.cs

@@ -7,7 +7,7 @@ namespace UCalc.Pages
     public partial class HousePage
     {
         public Window ParentWindow { get; set; }
-        public HouseModel Model { get; set; }
+        public HouseProperty House { get; set; }
 
         public HousePage()
         {
@@ -16,25 +16,25 @@ namespace UCalc.Pages
 
         private void OnAddFlatClick(object sender, RoutedEventArgs e)
         {
-            Model.AddFlat();
+            House.Flats.Add();
         }
 
         private void OnFlatDeleteClick(object sender, RoutedEventArgs e)
         {
-            var flatModel = (FlatModel) ((HighlightButton) sender).DataContext;
+            var flat = (FlatProperty) ((HighlightButton) sender).DataContext;
 
-            if (MessageBox.Show($"Möchten Sie die Wohnung \"{flatModel.Data.Name}\" wirlick löschen?", "Löschen?",
+            if (MessageBox.Show($"Möchten Sie die Wohnung \"{flat.Name.Value}\" wirlick löschen?", "Löschen?",
                 MessageBoxButton.YesNo, MessageBoxImage.Question) == MessageBoxResult.Yes)
             {
-                Model.RemoveFlat(flatModel);
+                House.Flats.Remove(flat);
             }
         }
 
         private void OnFlatEditClick(object sender, RoutedEventArgs e)
         {
-            var flatModel = (FlatModel) ((HighlightButton) sender).DataContext;
+            var flat = (FlatProperty) ((HighlightButton) sender).DataContext;
 
-            new FlatWindow(flatModel) {Owner = ParentWindow}.ShowDialog();
+            new FlatWindow(flat) {Owner = ParentWindow}.ShowDialog();
         }
     }
 }

ucalc/Pages/LandlordPage.xaml

@@ -21,7 +21,7 @@
 
                 <ComboBox Margin="0, 0, 28, 0"
                           ItemsSource="{x:Static local:Constants.SalutationStrs}" 
-                          SelectedIndex="{Binding Path=Model.Salutation.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}"/> 
+                          SelectedIndex="{Binding Path=Landlord.Salutation.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}"/> 
             </DockPanel>
 
             <DockPanel Margin="12, 12, 12, 0">
@@ -33,12 +33,12 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.Name.Errors, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
+                                    Property="{Binding Path=Landlord.Name, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.Name.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=Landlord.Name.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
             <DockPanel Margin="12, 8, 12, 0">
@@ -50,12 +50,12 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.Phone.Errors, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
+                                    Property="{Binding Path=Landlord.Phone, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.Phone.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=Landlord.Phone.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
             <DockPanel Margin="12, 8, 12, 0">
@@ -67,12 +67,12 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.MailAddress.Errors, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
+                                    Property="{Binding Path=Landlord.MailAddress, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.MailAddress.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=Landlord.MailAddress.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
             <controls:SectionHeader Header="Adresse des Eigentümers"
@@ -87,12 +87,12 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.Address.Model.Street.Errors, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
+                                    Property="{Binding Path=Landlord.Address.Street, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.Address.Model.Street.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=Landlord.Address.Street.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
             <DockPanel Margin="12, 8, 12, 0">
@@ -104,12 +104,12 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.Address.Model.HouseNumber.Errors, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
+                                    Property="{Binding Path=Landlord.Address.HouseNumber, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.Address.Model.HouseNumber.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=Landlord.Address.HouseNumber.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
             <DockPanel Margin="12, 8, 12, 0">
@@ -121,12 +121,12 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.Address.Model.City.Errors, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
+                                    Property="{Binding Path=Landlord.Address.City, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.Address.Model.City.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=Landlord.Address.City.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
             <DockPanel Margin="12, 8, 12, 0">
@@ -138,12 +138,12 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.Address.Model.Postcode.Errors, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
+                                    Property="{Binding Path=Landlord.Address.Postcode, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.Address.Model.Postcode.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=Landlord.Address.Postcode.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
             <controls:SectionHeader Header="Bankdaten des Eigentümers"
@@ -158,12 +158,12 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.BankAccount.Model.Iban.Errors, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
+                                    Property="{Binding Path=Landlord.BankAccount.Iban, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.BankAccount.Model.Iban.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=Landlord.BankAccount.Iban.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
             <DockPanel Margin="12, 8, 12, 0">
@@ -175,12 +175,12 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.BankAccount.Model.Bic.Errors, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
+                                    Property="{Binding Path=Landlord.BankAccount.Bic, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.BankAccount.Model.Bic.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=Landlord.BankAccount.Bic.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
             <DockPanel Margin="12, 8, 12, 12">
@@ -192,12 +192,12 @@
                 <controls:ErrorIcon Margin="12, 0, 0, 0"
                                     DockPanel.Dock="Right"
                                     VerticalAlignment="Center"
-                                    Errors="{Binding Path=Model.BankAccount.Model.BankName.Errors, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
+                                    Property="{Binding Path=Landlord.BankAccount.BankName, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}}" />
 
                 <TextBox
                     VerticalAlignment="Center"
                     MinHeight="22"
-                    Text="{Binding Path=Model.BankAccount.Model.BankName.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
+                    Text="{Binding Path=Landlord.BankAccount.BankName.Value, RelativeSource={RelativeSource AncestorType=pages:LandlordPage}, UpdateSourceTrigger=PropertyChanged}" />
             </DockPanel>
 
         </StackPanel>

ucalc/Pages/LandlordPage.xaml.cs

@@ -4,7 +4,7 @@ namespace UCalc.Pages
 {
     public partial class LandlordPage
     {
-        public LandlordModel Model { get; set; }
+        public LandlordProperty Landlord { get; set; }
 
         public LandlordPage()
         {

ucalc/Pages/SideBar.xaml

@@ -119,7 +119,7 @@
             <controls:ErrorCounter DockPanel.Dock="Right"
                                    Margin="0, 12, 12, 12"
                                    VerticalAlignment="Center"
-                                   Model="{Binding Path=Model.LandlordModel, RelativeSource={RelativeSource AncestorType=pages:SideBar}}"/>
+                                   Property="{Binding Path=Model.Root.Landlord, RelativeSource={RelativeSource AncestorType=pages:SideBar}}"/>
 
             <Label Content="Eigentümer"
                    Margin="0, 12, 12, 12"
@@ -156,7 +156,7 @@
             <controls:ErrorCounter DockPanel.Dock="Right"
                                    Margin="0, 12, 12, 12"
                                    VerticalAlignment="Center"
-                                   Model="{Binding Path=Model.HouseModel, RelativeSource={RelativeSource AncestorType=pages:SideBar}}"/>
+                                   Property="{Binding Path=Model.Root.House, RelativeSource={RelativeSource AncestorType=pages:SideBar}}"/>
 
             <Label Content="Haus"
                    Margin="0, 12, 12, 12"
@@ -190,6 +190,11 @@
                 </Canvas>
             </Viewbox>
 
+            <controls:ErrorCounter DockPanel.Dock="Right"
+                                   Margin="0, 12, 12, 12"
+                                   VerticalAlignment="Center"
+                                   Property="{Binding Path=Model.Root.Tenants, RelativeSource={RelativeSource AncestorType=pages:SideBar}}"/>
+
             <Label Content="Mieter"
                    Margin="0, 12, 12, 12"
                    VerticalAlignment="Center"

ucalc/Pages/SideBar.xaml.cs

@@ -9,7 +9,7 @@ namespace UCalc.Pages
     public partial class SideBar
     {
         public TabControl TabControl { get; set; }
-        public BillingModel Model { get; set; }
+        public Model Model { get; set; }
 
         public SideBar()
         {

ucalc/Pages/TenantsPage.xaml

@@ -3,7 +3,98 @@
       xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
       xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
       xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
-      xmlns:local="clr-namespace:UCalc.Pages"
+      xmlns:controls="clr-namespace:UCalc.Controls"
+      xmlns:local="clr-namespace:UCalc"
+      xmlns:pages="clr-namespace:UCalc.Pages"
       mc:Ignorable="d">
-    <Grid />
+
+    <Page.Resources>
+        <controls:EmptyMultiPropertyToVisibilityConverter x:Key="EmptyMultiPropertyToVisibilityConverter" />
+    </Page.Resources>
+
+    <DockPanel>
+        <DockPanel DockPanel.Dock="Top"
+                   Margin="0, 0, 0, 8">
+            <controls:ErrorIcon Margin="0, 0, 12, 0"
+                                DockPanel.Dock="Right"
+                                VerticalAlignment="Center"
+                                Property="{Binding Path=Tenants, RelativeSource={RelativeSource AncestorType=pages:TenantsPage}}"
+                                Visibility="{Binding Path=Tenants.Count, RelativeSource={RelativeSource AncestorType=pages:TenantsPage}, Converter={StaticResource EmptyMultiPropertyToVisibilityConverter}}" />
+
+            <controls:HighlightButton Margin="12, 0, 12, 0"
+                                      HighlightForeground="{x:Static local:Constants.SubMainColor}"
+                                      HighlightBackground="{x:Static local:Constants.MainColor}"
+                                      Click="OnAddTenantClick">
+                <Viewbox Width="24"
+                         Height="24"
+                         Margin="12, 12, 6, 12"
+                         Stretch="Uniform">
+                    <Canvas Width="512" Height="512">
+                        <Canvas.RenderTransform>
+                            <TranslateTransform X="0" Y="0" />
+                        </Canvas.RenderTransform>
+                        <Path>
+                            <Path.Data>
+                                <PathGeometry
+                                    Figures="M256 8C119 8 8 119 8 256s111 248 248 248 248-111 248-248S393 8 256 8zm144 276c0 6.6-5.4 12-12 12h-92v92c0 6.6-5.4 12-12 12h-56c-6.6 0-12-5.4-12-12v-92h-92c-6.6 0-12-5.4-12-12v-56c0-6.6 5.4-12 12-12h92v-92c0-6.6 5.4-12 12-12h56c6.6 0 12 5.4 12 12v92h92c6.6 0 12 5.4 12 12v56z"
+                                    FillRule="NonZero" />
+                            </Path.Data>
+                        </Path>
+                    </Canvas>
+                </Viewbox>
+
+                <Label Content="Mieter hinzufügen"
+                       Margin="0, 12, 12, 12" />
+            </controls:HighlightButton>
+        </DockPanel>
+
+        <ScrollViewer HorizontalScrollBarVisibility="Disabled"
+                      VerticalScrollBarVisibility="Auto">
+            <ItemsControl
+                ItemsSource="{Binding Path=Tenants, RelativeSource={RelativeSource AncestorType=pages:TenantsPage}}"
+                Margin="12, 0, 12, 12">
+                <ItemsControl.ItemTemplate>
+                    <DataTemplate>
+                        <DockPanel>
+                            <controls:HighlightButton DockPanel.Dock="Right"
+                                                      HighlightForeground="Red"
+                                                      HighlightBackground="White"
+                                                      Click="OnTenantDeleteClick">
+                                <Viewbox Width="24"
+                                         Height="24"
+                                         Margin="8, 12, 8, 12"
+                                         Stretch="Uniform">
+                                    <Canvas Width="448" Height="512">
+                                        <Canvas.RenderTransform>
+                                            <TranslateTransform X="0" Y="0" />
+                                        </Canvas.RenderTransform>
+                                        <Path>
+                                            <Path.Data>
+                                                <PathGeometry
+                                                    Figures="M32 464a48 48 0 0 0 48 48h288a48 48 0 0 0 48-48V128H32zm272-256a16 16 0 0 1 32 0v224a16 16 0 0 1-32 0zm-96 0a16 16 0 0 1 32 0v224a16 16 0 0 1-32 0zm-96 0a16 16 0 0 1 32 0v224a16 16 0 0 1-32 0zM432 32H312l-9.4-18.7A24 24 0 0 0 281.1 0H166.8a23.72 23.72 0 0 0-21.4 13.3L136 32H16A16 16 0 0 0 0 48v32a16 16 0 0 0 16 16h416a16 16 0 0 0 16-16V48a16 16 0 0 0-16-16z"
+                                                    FillRule="NonZero" />
+                                            </Path.Data>
+                                        </Path>
+                                    </Canvas>
+                                </Viewbox>
+                            </controls:HighlightButton>
+
+                            <controls:HighlightButton HighlightForeground="{x:Static local:Constants.SubMainColor}"
+                                                      HighlightBackground="{x:Static local:Constants.MainColor}"
+                                                      Click="OnTenantEditClick">
+
+                                <controls:ErrorIcon Property="{Binding .}"
+                                                    DockPanel.Dock="Left"
+                                                    Margin="12, 12, 8, 12" />
+
+                                <Label Content="{Binding Name.Value}"
+                                       VerticalAlignment="Center" />
+                            </controls:HighlightButton>
+                        </DockPanel>
+                    </DataTemplate>
+                </ItemsControl.ItemTemplate>
+            </ItemsControl>
+        </ScrollViewer>
+    </DockPanel>
+
 </Page>

ucalc/Pages/TenantsPage.xaml.cs

@@ -1,12 +1,41 @@
-using System.Windows.Controls;
+using System.Windows;
+using UCalc.Controls;
+using UCalc.Models;
 
 namespace UCalc.Pages
 {
-    public partial class TenantsPage : Page
+    public partial class TenantsPage
     {
+        public Window ParentWindow { get; set; }
+        public TenantsProperty Tenants { get; set; }
+        public HouseProperty House { get; set; }
+
         public TenantsPage()
         {
             InitializeComponent();
         }
+
+        private void OnAddTenantClick(object sender, RoutedEventArgs e)
+        {
+            Tenants.Add();
+        }
+
+        private void OnTenantDeleteClick(object sender, RoutedEventArgs e)
+        {
+            var tenant = (TenantProperty) ((HighlightButton) sender).DataContext;
+
+            if (MessageBox.Show($"Möchten Sie den Mieter \"{tenant.Name.Value}\" wirlick löschen?", "Löschen?",
+                MessageBoxButton.YesNo, MessageBoxImage.Question) == MessageBoxResult.Yes)
+            {
+                Tenants.Remove(tenant);
+            }
+        }
+
+        private void OnTenantEditClick(object sender, RoutedEventArgs e)
+        {
+            var tenant = (TenantProperty) ((HighlightButton) sender).DataContext;
+
+            new TenantWindow(tenant, House) {Owner = ParentWindow}.ShowDialog();
+        }
     }
 }

ucalc/TenantWindow.xaml

@@ -0,0 +1,253 @@
+<Window x:Class="UCalc.TenantWindow"
+        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+        xmlns:local="clr-namespace:UCalc"
+        xmlns:controls="clr-namespace:UCalc.Controls"
+        mc:Ignorable="d"
+        Title="Mieter bearbeiten"
+        Width="500"
+        Height="600"
+        MinWidth="400"
+        MinHeight="190"
+        WindowStartupLocation="CenterOwner"
+        ShowInTaskbar="False">
+
+    <Window.Resources>
+        <controls:FlatToRentedConverter x:Key="FlatToRentedConverter" />
+        <controls:DatePickerTextToDateTimeConverter x:Key="DatePickerTextToDateTimeConverter" />
+    </Window.Resources>
+
+    <DockPanel>
+        <StackPanel DockPanel.Dock="Bottom">
+            <Separator Margin="0, 12, 0, 0"
+                       Background="{x:Static local:Constants.SubMainColor}" />
+
+            <DockPanel LastChildFill="False">
+                <Button DockPanel.Dock="Right"
+                        MinWidth="100"
+                        MinHeight="24"
+                        Margin="12"
+                        Content="OK"
+                        Click="OnOkClick" />
+            </DockPanel>
+        </StackPanel>
+
+        <ScrollViewer HorizontalScrollBarVisibility="Disabled"
+                      VerticalScrollBarVisibility="Auto">
+            <StackPanel>
+                <controls:SectionHeader Header="Allgemeine Informationen" />
+
+                <DockPanel Margin="12, 12, 12, 0">
+                    <Label DockPanel.Dock="Left"
+                           Content="Anrede:"
+                           Width="180"
+                           Foreground="{x:Static local:Constants.SubMainColor}" />
+
+                    <ComboBox Margin="0, 0, 28, 0"
+                              ItemsSource="{x:Static local:Constants.SalutationStrs}"
+                              SelectedIndex="{Binding Path=Tenant.Salutation.Value, RelativeSource={RelativeSource AncestorType=local:TenantWindow}}" />
+                </DockPanel>
+
+                <DockPanel Margin="12, 8, 12, 0">
+                    <Label DockPanel.Dock="Left"
+                           Content="Name:"
+                           Width="180"
+                           Foreground="{x:Static local:Constants.SubMainColor}" />
+
+                    <controls:ErrorIcon Margin="12, 0, 0, 0"
+                                        DockPanel.Dock="Right"
+                                        VerticalAlignment="Center"
+                                        Property="{Binding Path=Tenant.Name, RelativeSource={RelativeSource AncestorType=local:TenantWindow}}" />
+
+                    <TextBox
+                        VerticalAlignment="Center"
+                        MinHeight="22"
+                        Text="{Binding Path=Tenant.Name.Value, RelativeSource={RelativeSource AncestorType=local:TenantWindow}, UpdateSourceTrigger=PropertyChanged}" />
+                </DockPanel>
+
+                <DockPanel Margin="12, 8, 12, 0">
+                    <Label DockPanel.Dock="Left"
+                           Content="Personenanzahl:"
+                           Width="180"
+                           Foreground="{x:Static local:Constants.SubMainColor}" />
+
+                    <controls:ErrorIcon Margin="12, 0, 0, 0"
+                                        DockPanel.Dock="Right"
+                                        VerticalAlignment="Center"
+                                        Property="{Binding Path=Tenant.PersonCount, RelativeSource={RelativeSource AncestorType=local:TenantWindow}}" />
+
+                    <TextBox
+                        VerticalAlignment="Center"
+                        MinHeight="22"
+                        Text="{Binding Path=Tenant.PersonCount.Value, RelativeSource={RelativeSource AncestorType=local:TenantWindow}, UpdateSourceTrigger=PropertyChanged}" />
+                </DockPanel>
+
+                <controls:SectionHeader Header="Bankdaten"
+                                        Margin="0, 12, 0, 0" />
+
+                <DockPanel Margin="12, 8, 12, 0">
+                    <Label DockPanel.Dock="Left"
+                           Content="IBAN:"
+                           Width="180"
+                           Foreground="{x:Static local:Constants.SubMainColor}" />
+
+                    <controls:ErrorIcon Margin="12, 0, 0, 0"
+                                        DockPanel.Dock="Right"
+                                        VerticalAlignment="Center"
+                                        Property="{Binding Path=Tenant.BankAccount.Iban, RelativeSource={RelativeSource AncestorType=local:TenantWindow}}" />
+
+                    <TextBox
+                        VerticalAlignment="Center"
+                        MinHeight="22"
+                        Text="{Binding Path=Tenant.BankAccount.Iban.Value, RelativeSource={RelativeSource AncestorType=local:TenantWindow}, UpdateSourceTrigger=PropertyChanged}" />
+                </DockPanel>
+
+                <DockPanel Margin="12, 8, 12, 0">
+                    <Label DockPanel.Dock="Left"
+                           Content="BIC:"
+                           Width="180"
+                           Foreground="{x:Static local:Constants.SubMainColor}" />
+
+                    <controls:ErrorIcon Margin="12, 0, 0, 0"
+                                        DockPanel.Dock="Right"
+                                        VerticalAlignment="Center"
+                                        Property="{Binding Path=Tenant.BankAccount.Bic, RelativeSource={RelativeSource AncestorType=local:TenantWindow}}" />
+
+                    <TextBox
+                        VerticalAlignment="Center"
+                        MinHeight="22"
+                        Text="{Binding Path=Tenant.BankAccount.Bic.Value, RelativeSource={RelativeSource AncestorType=local:TenantWindow}, UpdateSourceTrigger=PropertyChanged}" />
+                </DockPanel>
+
+                <DockPanel Margin="12, 8, 12, 0">
+                    <Label DockPanel.Dock="Left"
+                           Content="Name der Bank:"
+                           Width="180"
+                           Foreground="{x:Static local:Constants.SubMainColor}" />
+
+                    <controls:ErrorIcon Margin="12, 0, 0, 0"
+                                        DockPanel.Dock="Right"
+                                        VerticalAlignment="Center"
+                                        Property="{Binding Path=Tenant.BankAccount.BankName, RelativeSource={RelativeSource AncestorType=local:TenantWindow}}" />
+
+                    <TextBox
+                        VerticalAlignment="Center"
+                        MinHeight="22"
+                        Text="{Binding Path=Tenant.BankAccount.BankName.Value, RelativeSource={RelativeSource AncestorType=local:TenantWindow}, UpdateSourceTrigger=PropertyChanged}" />
+                </DockPanel>
+
+                <controls:SectionHeader Header="Ein- und Auszug"
+                                        Margin="0, 12, 0, 0" />
+
+                <DockPanel Margin="12, 8, 12, 0">
+                    <Label DockPanel.Dock="Left"
+                           Content="Einzug am:"
+                           Width="180"
+                           Foreground="{x:Static local:Constants.SubMainColor}" />
+
+                    <controls:ErrorIcon Margin="12, 0, 0, 0"
+                                        DockPanel.Dock="Right"
+                                        VerticalAlignment="Center"
+                                        Property="{Binding Path=Tenant.EntryDate, RelativeSource={RelativeSource AncestorType=local:TenantWindow}}" />
+<!-- TODO                                 DisplayDateStart="{}" -->
+                    <DatePicker VerticalAlignment="Center"
+                                MinHeight="22"
+                                Text="{Binding Path=Tenant.EntryDate.Value, RelativeSource={RelativeSource AncestorType=local:TenantWindow}, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay, Converter={StaticResource DatePickerTextToDateTimeConverter}}" />
+                </DockPanel>
+
+                <DockPanel Margin="12, 8, 12, 0">
+                    <Label DockPanel.Dock="Left"
+                           Content="Auszug am:"
+                           Width="180"
+                           Foreground="{x:Static local:Constants.SubMainColor}" />
+
+                    <controls:ErrorIcon Margin="12, 0, 0, 0"
+                                        DockPanel.Dock="Right"
+                                        VerticalAlignment="Center"
+                                        Property="{Binding Path=Tenant.DepartureDate, RelativeSource={RelativeSource AncestorType=local:TenantWindow}}" />
+
+                    <DatePicker VerticalAlignment="Center"
+                                MinHeight="22"
+                                Text="{Binding Path=Tenant.DepartureDate.Value, RelativeSource={RelativeSource AncestorType=local:TenantWindow}, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay, Converter={StaticResource DatePickerTextToDateTimeConverter}}" />
+                </DockPanel>
+
+                <controls:SectionHeader Header="Gemietete Wohnungen"
+                                        Margin="0, 12, 0, 0" />
+
+                <DockPanel Margin="12, 8, 12, 0">
+                    <controls:ErrorIcon Margin="12, 0, 0, 0"
+                                        DockPanel.Dock="Right"
+                                        VerticalAlignment="Center"
+                                        Property="{Binding Path=Tenant.RentedFlats, RelativeSource={RelativeSource AncestorType=local:TenantWindow}}" />
+
+                    <ListBox Height="120"
+                             ItemsSource="{Binding Path=House.Flats, RelativeSource={RelativeSource AncestorType=local:TenantWindow}}">
+                        <ListBox.ItemTemplate>
+                            <DataTemplate>
+                                <CheckBox Content="{Binding Name.Value}"
+                                          IsChecked="{Binding Path=., Converter={StaticResource FlatToRentedConverter}, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}"
+                                          Checked="OnFlatChecked"
+                                          Unchecked="OnFlatUnchecked"/>
+                            </DataTemplate>
+                        </ListBox.ItemTemplate>
+                    </ListBox>
+                </DockPanel>
+
+                <controls:SectionHeader Header="Sonstiges"
+                                        Margin="0, 12, 0, 0" />
+
+                <DockPanel Margin="12, 8, 12, 0">
+                    <Label DockPanel.Dock="Left"
+                           Content="Bereits bezahlt:"
+                           Width="180"
+                           Foreground="{x:Static local:Constants.SubMainColor}" />
+
+                    <controls:ErrorIcon Margin="12, 0, 0, 0"
+                                        DockPanel.Dock="Right"
+                                        VerticalAlignment="Center"
+                                        Property="{Binding Path=Tenant.PaidRent, RelativeSource={RelativeSource AncestorType=local:TenantWindow}}" />
+
+                    <TextBox VerticalAlignment="Center"
+                             MinHeight="22"
+                             Text="{Binding Path=Tenant.PaidRent.Value, RelativeSource={RelativeSource AncestorType=local:TenantWindow}, UpdateSourceTrigger=PropertyChanged}" />
+                </DockPanel>
+
+                <DockPanel Margin="12, 8, 12, 0">
+                    <Label DockPanel.Dock="Left"
+                           Content="Nachricht 1:"
+                           Width="180"
+                           Foreground="{x:Static local:Constants.SubMainColor}" />
+
+                    <controls:ErrorIcon Margin="12, 0, 0, 0"
+                                        DockPanel.Dock="Right"
+                                        VerticalAlignment="Center"
+                                        Property="{Binding Path=Tenant.CustomMessage1, RelativeSource={RelativeSource AncestorType=local:TenantWindow}}" />
+
+                    <TextBox VerticalAlignment="Center"
+                             MinHeight="22"
+                             Text="{Binding Path=Tenant.CustomMessage1.Value, RelativeSource={RelativeSource AncestorType=local:TenantWindow}, UpdateSourceTrigger=PropertyChanged}" />
+                </DockPanel>
+
+                <DockPanel Margin="12, 8, 12, 0">
+                    <Label DockPanel.Dock="Left"
+                           Content="Nachricht 2:"
+                           Width="180"
+                           Foreground="{x:Static local:Constants.SubMainColor}" />
+
+                    <controls:ErrorIcon Margin="12, 0, 0, 0"
+                                        DockPanel.Dock="Right"
+                                        VerticalAlignment="Center"
+                                        Property="{Binding Path=Tenant.CustomMessage2, RelativeSource={RelativeSource AncestorType=local:TenantWindow}}" />
+
+                    <TextBox VerticalAlignment="Center"
+                             MinHeight="22"
+                             Text="{Binding Path=Tenant.CustomMessage2.Value, RelativeSource={RelativeSource AncestorType=local:TenantWindow}, UpdateSourceTrigger=PropertyChanged}" />
+                </DockPanel>
+
+            </StackPanel>
+        </ScrollViewer>
+    </DockPanel>
+
+</Window>

ucalc/TenantWindow.xaml.cs

@@ -0,0 +1,41 @@
+using System.Windows;
+using System.Windows.Controls;
+using UCalc.Controls;
+using UCalc.Models;
+
+namespace UCalc
+{
+    public partial class TenantWindow
+    {
+        public TenantProperty Tenant { get; }
+        public HouseProperty House { get; }
+
+        public TenantWindow(TenantProperty tenant, HouseProperty house)
+        {
+            Tenant = tenant;
+            House = house;
+            InitializeComponent();
+
+            ((FlatToRentedConverter) FindResource("FlatToRentedConverter")).Tenant = Tenant;
+        }
+
+        private void OnOkClick(object sender, RoutedEventArgs e)
+        {
+            Close();
+        }
+
+        private void OnFlatChecked(object sender, RoutedEventArgs e)
+        {
+            var flat = (FlatProperty) ((CheckBox) sender).DataContext;
+
+            Tenant.RentedFlats.Add(flat);
+        }
+
+        private void OnFlatUnchecked(object sender, RoutedEventArgs e)
+        {
+            var flat = (FlatProperty) ((CheckBox) sender).DataContext;
+
+            Tenant.RentedFlats.Remove(flat);
+        }
+    }
+}

ucalc/ucalc.csproj

@@ -40,6 +40,9 @@
         <Page Update="FlatWindow.xaml">
             <Generator></Generator>
         </Page>
+        <Page Update="TenantWindow.xaml">
+            <Generator></Generator>
+        </Page>
     </ItemGroup>
 
     <ItemGroup>
@@ -76,6 +79,9 @@
         <Compile Update="FlatWindow.xaml.cs">
             <DependentUpon>FlatWindow.xaml</DependentUpon>
         </Compile>
+        <Compile Update="TenantWindow.xaml.cs">
+            <DependentUpon>TenantWindow.xaml</DependentUpon>
+        </Compile>
     </ItemGroup>
 
 </Project>