WindowClosingBehavior.cs

using System;
using System.ComponentModel;
using System.Windows;
using System.Windows.Input;

/// <summary>
/// This module is included here because it can be used in all WPF projects to
/// manage the closing behavior of the main window; e.g., determing whether there
/// is a need to save before exiting, preventing exiting on some conditions, etc.
/// </summary>

namespace Common
{
    public class WindowClosingBehavior
    {
        public static ICommand GetClosed(DependencyObject obj)
        {
            return (ICommand)obj.GetValue(ClosedProperty);
        }

        public static void SetClosed(DependencyObject obj, ICommand value)
        {
            obj.SetValue(ClosedProperty, value);
        }

        public static readonly DependencyProperty ClosedProperty
            = DependencyProperty.RegisterAttached(
            "Closed", typeof(ICommand), typeof(WindowClosingBehavior),
            new UIPropertyMetadata(new PropertyChangedCallback(ClosedChanged)));

        private static void ClosedChanged(
          DependencyObject target, DependencyPropertyChangedEventArgs e)
        {
            Window window = target as Window;

            if (window != null)
            {
                if (e.NewValue != null)
                {
                    window.Closed += Window_Closed;
                }
                else
                {
                    window.Closed -= Window_Closed;
                }
            }
        }

        public static ICommand GetClosing(DependencyObject obj)
        {
            return (ICommand)obj.GetValue(ClosingProperty);
        }

        public static void SetClosing(DependencyObject obj, ICommand value)
        {
            obj.SetValue(ClosingProperty, value);
        }

        public static readonly DependencyProperty ClosingProperty
            = DependencyProperty.RegisterAttached(
            "Closing", typeof(ICommand), typeof(WindowClosingBehavior),
            new UIPropertyMetadata(new PropertyChangedCallback(ClosingChanged)));

        private static void ClosingChanged(
          DependencyObject target, DependencyPropertyChangedEventArgs e)
        {
            Window window = target as Window;

            if (window != null)
            {
                if (e.NewValue != null)
                {
                    window.Closing += Window_Closing;
                }
                else
                {
                    window.Closing -= Window_Closing;
                }
            }
        }

        public static ICommand GetCancelClosing(DependencyObject obj)
        {
            return (ICommand)obj.GetValue(CancelClosingProperty);
        }

        public static void SetCancelClosing(DependencyObject obj, ICommand value)
        {
            obj.SetValue(CancelClosingProperty, value);
        }

        public static readonly DependencyProperty CancelClosingProperty
            = DependencyProperty.RegisterAttached(
            "CancelClosing", typeof(ICommand), typeof(WindowClosingBehavior));

        static void Window_Closed(object sender, EventArgs e)
        {
            ICommand closed = GetClosed(sender as Window);
            if (closed != null)
            {
                closed.Execute(null);
            }
        }

        static void Window_Closing(object sender, CancelEventArgs e)
        {
            ICommand closing = GetClosing(sender as Window);
            if (closing != null)
            {
                if (closing.CanExecute(null))
                {
                    closing.Execute(null);
                }
                else
                {
                    ICommand cancelClosing = GetCancelClosing(sender as Window);
                    if (cancelClosing != null)
                    {
                        cancelClosing.Execute(null);
                    }

                    e.Cancel = true;
                }
            }
        }
    }
}