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MVVM # Episode 1

, 3 Dec 2013 CPOL
Using an extended MVVM pattern for real world LOB applications: Part 1
CustomerMaintenance
Controllers
Base Classes
bin
Release
Controllers.csproj.vs10x
Properties
CustomerMaintenance
bin
Debug
CustomerMaintenance.vshost.exe
CustomerMaintenance.vshost.exe.manifest
Release
CustomerMaintenance.csproj.user
CustomerMaintenance.csproj.vs10x
Properties
Messengers
bin
Release
Messengers.csproj.vs10x
Properties
Model
bin
Debug
Release
Models.csproj.vs10x
Properties
Service
bin
Release
Properties
Services.csproj.vs10x
ViewModel
BaseClasses
bin
Release
Properties
ViewData
ViewModels.csproj.vs10x
Views
Base Classes
bin
Release
Converters
DesignTimeData
Properties
Views.csproj.vs10x
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
	}
}

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About the Author

_Maxxx_
Software Developer (Senior) Devo
Australia Australia
Software developer par excellence,sometime artist, teacher, musician, husband, father and half-life 2 player (in no particular order either of preference or ability)
Started programming aged about 16 on a Commodore Pet.
Self-taught 6500 assembler - wrote Missile Command on the Pet (impressive, if I say so myself, on a text-only screen!)
Progressed to BBC Micro - wrote a number of prize-winning programs - including the best graphics application in one line of basic (it drew 6 multicoloured spheres viewed in perspective)
Trained with the MET Police as a COBOL programmer
Wrote platform game PooperPig which was top of the Ceefax Charts for a while in the UK
Did a number of software dev roles in COBOL
Progressed to Atari ST - learned 68000 assembler & write masked sprite engine.
Worked at Atari ST User magazine as Technical Editor - and was editor of Atari ST World for a while.
Moved on to IBM Mid range for work - working as team leader then project manager
Emigrated to Aus.
Learned RPG programming on the job (by having frequent coffee breaks with the wife!!)
Moved around a few RPG sites
Wrote for PC User magazine - was Shareware Magazine editor for a while.
Organised the first large-scale usage of the Internet in Australia through PC User magazine.
Moved from RPG to Delphi 1
Developed large applications in Delphi before moving on to VB .Net and C#
Became I.T. Manager - realised how boring paper pushing can be
And now I pretty much do .Net development in the daytime, while redeveloping PooperPig for the mobile market at night.

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