Layers Pattern in Practice

using System;
using System.Windows;
using System.Windows.Data;
using System.Globalization;

namespace BillPayManager
{
    /// <summary>
    /// Converts <c>null</c> values to <see cref="DependencyProperty.UnsetValue"/>.
    /// <remarks>
    /// This converter is intented for use in situations when the binding target
    /// does not correctly handle <c>null</c> values. This is the case for example
    /// with some WPF UI controls.
    /// </remarks>
    /// </summary>
    public class NullToUnsetConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return value ?? DependencyProperty.UnsetValue;
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            // No conversion applied
            return value;
        }
    }
}