MVVM # Episode 1

using System;
using System.Windows;
using System.Windows.Controls;
using ViewModels;


namespace Views
{
	/// <summary>
	/// A delegate to allow the window closed event to be handled (if required)
	/// </summary>
	/// <param name="o"></param>
	/// <param name="e"></param>
	public delegate void OnWindowClose(Object sender, EventArgs e);

	/// <summary>
	/// This is the basis of all views.
	/// It cannot be Abstract because of design time issues when it tries to instantiate this class.
	/// Note that this 'view' doesn't have any Xaml (because you can't inherit Xaml)
	/// </summary>
	public partial class BaseView : UserControl, IDisposable, IView
	{
		private ViewWindow viewWindow; // If shown on a window, the window in question
		private OnWindowClose onWindowClosed = null;

		#region Closing

		/// <summary>
		/// The view is closing, so clean up references
		/// </summary>
		public void ViewClosed()
		{
			// In order to handle the case where the user closes the window (rather than us controlling the close via a ViewModel)
			// we need to check that the DataContext isn't null (which would mean this ViewClosed has already been done)
			if (DataContext != null)
			{
				((BaseViewModel)DataContext).ViewModelClosing -= ViewModelClosingHandler;
				((BaseViewModel)DataContext).ViewModelActivating -= ViewModelActivatingHandler;
				this.DataContext = null; // Make sure we don't have a reference to the VM any more.
			}

		}

		/// <summary>
		/// Handle the Window Closed event
		/// </summary>
		/// <param name="sender"></param>
		/// <param name="e"></param>
		void ViewsWindow_Closed(object sender, EventArgs e)
		{

			if (onWindowClosed != null)
			{
				onWindowClosed(sender, e);
			}
			((BaseViewModel)DataContext).CloseViewModel(false);
		}
		#endregion

		#region IView implementations
		/// <summary>
		/// Tell the View to close itself. Handle the case where we're in a window and the window needs closing.
		/// </summary>
		/// <param name="dialogResult"></param>
		public void ViewModelClosingHandler(bool? dialogResult)
		{
			if (viewWindow == null)
			{
				System.Windows.Controls.Panel panel = this.Parent as System.Windows.Controls.Panel;
				if (panel != null)
				{
					panel.Children.Remove(this);
				}
			}
			else
			{
				viewWindow.Closed -= ViewsWindow_Closed;

				if (viewWindow.IsDialogWindow)
				{
					// If the window is a Dialog and is not actiuve it must be in the process of being closed
					if (viewWindow.IsActive)
					{
						viewWindow.DialogResult = dialogResult;
					}
				}
				else
				{
					viewWindow.Close();
				}
				viewWindow = null;
			}
			// Process the ViewClosed method to cater for if this has been instigated by the user closing a window, rather than by
			// the close being instigated by a ViewModel
			ViewClosed();
		}

		public void ViewModelActivatingHandler()
		{
			if (viewWindow != null)
			{
				viewWindow.Activate();
			}
		}
		#endregion


		#region Constructor
		public BaseView()
		{
		}
		#endregion
		#region Window
		/// <summary>
		/// The Window on which the View is displayed (if it is displayed on a Window)
		/// The Window will be created by the View on demand (if required) or may be 
		/// supplied by the application.
		/// </summary>
		private ViewWindow ViewWindow
		{
			get
			{
				if (viewWindow == null)
				{
					viewWindow = new ViewWindow();
					viewWindow.Closed += ViewsWindow_Closed;

				}
				return viewWindow;
			}
		}
		#endregion

		#region Showing methods
		/// <summary>
		/// Show this control in a window, sized to fit, with this title
		/// </summary>
		/// <param name="windowTitle"></param>
		public void ShowInWindow(bool modal, string windowTitle)
		{
			ShowInWindow(modal, windowTitle, 0, 0, Dock.Top, null);
		}

		/// <summary>
		/// Show this control in an existing window, by default docked top.
		/// </summary>
		/// <param name="window"></param>
		public void ShowInWindow(bool modal, ViewWindow window)
		{
			ShowInWindow(modal, window, window.Title, window.Width, window.Height, Dock.Top, null);
		}

		/// <summary>
		/// Maximum Flexibility of Window Definition version of Show In Window
		/// </summary>
		/// <param name="window">THe Window in which to show this View</param>
		/// <param name="windowTitle">A Title for the Window</param>
		/// <param name="windowWidth">The Width of the Window</param>
		/// <param name="windowHeight">The Height of the Window</param>
		/// <param name="dock">How should the View be Docked</param>
		/// <param name="onWindowClosed">Event handler for when the window is closed</param>
		public void ShowInWindow(bool modal, ViewWindow window, string windowTitle, double windowWidth, double windowHeight, Dock dock, OnWindowClose onWindowClose)
		{
			this.onWindowClosed = onWindowClose;

			viewWindow = window;
			viewWindow.Title = windowTitle;

			DockPanel.SetDock(this, dock);
			// The viewWindow must have a dockPanel called WindowDockPanel. If you want to change this to use some other container on the window, then
			// the below code should be the only place it needs to be changed.
			viewWindow.WindowDockPanel.Children.Add(this);

			if (windowWidth == 0 && windowHeight == 0)
			{
				viewWindow.SizeToContent = SizeToContent.WidthAndHeight;
			}
			else
			{
				viewWindow.SizeToContent = SizeToContent.Manual;
				viewWindow.Width = windowWidth;
				viewWindow.Height = windowHeight;
			}

			if (modal)
			{
				viewWindow.ShowDialog();
			}
			else
			{
				viewWindow.Show();
			}
		}

		/// <summary>
		/// Show the View in a New Window
		/// </summary>
		/// <param name="windowTitle">Give the Window a Title</param>
		/// <param name="windowWidth">Set the Window's Width</param>
		/// <param name="windowHeight">Set the Window's Height</param>
		/// <param name="dock">How to Dock the View in the Window</param>
		/// <param name="onWindowClosed">Event handler for when the Window closes</param>
		public void ShowInWindow(bool modal, string windowTitle, double windowWidth, double windowHeight, Dock dock, OnWindowClose onWindowClose)
		{
			ShowInWindow(modal, ViewWindow, windowTitle, windowWidth, windowHeight, dock, onWindowClose);
		}
		#endregion
		#region IDisposable Members

		void IDisposable.Dispose()
		{
			// Remove any events from our window to prevent any memory leakage.
			if (viewWindow != null)
			{
				viewWindow.Closed -= this.ViewsWindow_Closed;
			}
		}

		#endregion
	}
}