ucalc/ucalc/Controls/Converters.cs

using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Data;

namespace UCalc.Controls
{
    public class ErrorsToVisibilityConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.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)
        {
            throw new InvalidOperationException();
        }
    }

    public class ErrorsToInVisibilityConverter : IValueConverter
    {
        private readonly ErrorsToVisibilityConverter _converter = new ErrorsToVisibilityConverter();

        public object Convert(object value, Type targetType, object parameter, System.Globalization.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)
        {
            throw new InvalidOperationException();
        }
    }


    public class ErrorCountToVisibilityConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            return (int?) value != 0 ? Visibility.Visible : Visibility.Collapsed;
        }

        public object ConvertBack(object value, Type targetType, object parameter,
            System.Globalization.CultureInfo culture)
        {
            throw new InvalidOperationException();
        }
    }
}