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WPF Control Factory

, 20 Apr 2010 CPOL
This article explains some advantages and disadvantages of factories, and shows one to use for generating WPF Controls.
WpfControlsAndSample.zip
WpfControlsAndSample
Pfz.ClassLibraries
Pfz
Caching
Collections
DataTypes
Extensions
Pfz.snk
Properties
Ranges
Threading
Pfz.WpfControls
BoundGridParts
Extensions
Pfz.WpfControls.snk
Properties
TypeConverters
WpfControlFactorySample
bin
Debug
Pfz.dll
Pfz.WpfControls.dll
WpfControlFactorySample.exe
Properties
Settings.settings
WpfControlFactorySample.suo
using System;

namespace Pfz.Caching
{
	/// <summary>
	/// Static class used to convert real (strong) delegates into weak
	/// delegates.
	/// </summary>
	public static class WeakDelegate
	{
		#region IsWeakDelegate
			/// <summary>
			/// Verifies if a handler is already a weak delegate.
			/// </summary>
			/// <param name="handler">The handler to verify.</param>
			/// <returns>true if the handler is already a weak delegate, false otherwise.</returns>
			public static bool IsWeakDelegate(Delegate handler)
			{
				return handler.Target != null && handler.Target is WeakDelegateBase;
			}
		#endregion
	
		#region From(Action)
			private sealed class WeakActionWrapper:
				WeakDelegateBase
			{
				internal WeakActionWrapper(Action handler):
					base(handler)
				{
				}
				internal void Execute()
				{
					Invoke(null);
				}
			}
			
			/// <summary>
			/// Creates a weak delegate from an Action delegate.
			/// </summary>
			public static Action From(Action strongHandler)
			{
				if (IsWeakDelegate(strongHandler))
					throw new ArgumentException("Your delegate is already a weak-delegate.");
				
				var wrapper = new WeakActionWrapper(strongHandler);
				return new Action(wrapper.Execute);
			}
		#endregion
		#region From(Action<T>)
			private sealed class WeakActionWrapper<T>:
				WeakDelegateBase
			{
				internal WeakActionWrapper(Action<T> handler):
					base(handler)
				{
				}
				internal void Execute(T parameter)
				{
					Invoke(new object[]{parameter});
				}
			}

			/// <summary>
			/// Creates a weak delegate from an Action&lt;T&gt; delegate.
			/// </summary>
			public static Action<T> From<T>(Action<T> strongHandler)
			{
				if (IsWeakDelegate(strongHandler))
					throw new ArgumentException("Your delegate is already a weak-delegate.");
					
				var wrapper = new WeakActionWrapper<T>(strongHandler);
				return new Action<T>(wrapper.Execute);
			}
		#endregion
		#region From(Action<T1, T2>)
			private sealed class WeakActionWrapper<T1, T2>:
				WeakDelegateBase
			{
				internal WeakActionWrapper(Action<T1, T2> handler):
					base(handler)
				{
				}
				internal void Execute(T1 parameter1, T2 parameter2)
				{
					Invoke(new object[]{parameter1, parameter2});
				}
			}

			/// <summary>
			/// Creates a weak delegate from an Action&lt;T1, T2&gt; delegate.
			/// </summary>
			public static Action<T1, T2> From<T1, T2>(Action<T1, T2> strongHandler)
			{
				if (IsWeakDelegate(strongHandler))
					throw new ArgumentException("Your delegate is already a weak-delegate.");
					
				var wrapper = new WeakActionWrapper<T1, T2>(strongHandler);
				return new Action<T1, T2>(wrapper.Execute);
			}
		#endregion
		#region From(Action<T1, T2, T3>)
			private sealed class WeakActionWrapper<T1, T2, T3>:
				WeakDelegateBase
			{
				internal WeakActionWrapper(Action<T1, T2, T3> handler):
					base(handler)
				{
				}
				internal void Execute(T1 parameter1, T2 parameter2, T3 parameter3)
				{
					Invoke(new object[]{parameter1, parameter2, parameter3});
				}
			}

			/// <summary>
			/// Creates a weak delegate from an Action&lt;T1, T2, T3&gt; delegate.
			/// </summary>
			public static Action<T1, T2, T3> From<T1, T2, T3>(Action<T1, T2, T3> strongHandler)
			{
				if (IsWeakDelegate(strongHandler))
					throw new ArgumentException("Your delegate is already a weak-delegate.");
					
				var wrapper = new WeakActionWrapper<T1, T2, T3>(strongHandler);
				return new Action<T1, T2, T3>(wrapper.Execute);
			}
		#endregion
		#region From(Action<T1, T2, T3, T4>)
			private sealed class WeakActionWrapper<T1, T2, T3, T4>:
				WeakDelegateBase
			{
				internal WeakActionWrapper(Action<T1, T2, T3, T4> handler):
					base(handler)
				{
				}
				internal void Execute(T1 parameter1, T2 parameter2, T3 parameter3, T4 parameter4)
				{
					Invoke(new object[]{parameter1, parameter2, parameter3, parameter4});
				}
			}

			/// <summary>
			/// Creates a weak delegate from an Action&lt;T1, T2, T3, T4&gt; delegate.
			/// </summary>
			public static Action<T1, T2, T3, T4> From<T1, T2, T3, T4>(Action<T1, T2, T3, T4> strongHandler)
			{
				if (IsWeakDelegate(strongHandler))
					throw new ArgumentException("Your delegate is already a weak-delegate.");
					
				var wrapper = new WeakActionWrapper<T1, T2, T3, T4>(strongHandler);
				return new Action<T1, T2, T3, T4>(wrapper.Execute);
			}
		#endregion
		
		#region From(EventHandler)
			private sealed class WeakEventHandlerWrapper:
				WeakDelegateBase
			{
				internal WeakEventHandlerWrapper(EventHandler handler):
					base(handler)
				{
				}
				internal void Execute(object sender, EventArgs e)
				{
					Invoke(new object[]{sender, e});
				}
			}

			/// <summary>
			/// Creates a weak delegate from an EventHandler delegate.
			/// </summary>
			public static EventHandler From(EventHandler strongHandler)
			{
				if (IsWeakDelegate(strongHandler))
					throw new ArgumentException("Your delegate is already a weak-delegate.");
					
				var wrapper = new WeakEventHandlerWrapper(strongHandler);
				return new EventHandler(wrapper.Execute);
			}
		#endregion
		#region From(EventHandler<TEventArgs>)
			private sealed class WeakEventHandlerWrapper<TEventArgs>:
				WeakDelegateBase
			where
				TEventArgs: EventArgs
			{
				internal WeakEventHandlerWrapper(EventHandler<TEventArgs> handler):
					base(handler)
				{
				}
				internal void Execute(object sender, TEventArgs e)
				{
					Invoke(new object[]{sender, e});
				}
			}

			/// <summary>
			/// Creates a weak delegate from an Action&lt;TEventArgs&gt; delegate.
			/// </summary>
			public static EventHandler<TEventArgs> From<TEventArgs>(EventHandler<TEventArgs> strongHandler)
			where
				TEventArgs: EventArgs
			{
				if (IsWeakDelegate(strongHandler))
					throw new ArgumentException("Your delegate is already a weak-delegate.");
					
				var wrapper = new WeakEventHandlerWrapper<TEventArgs>(strongHandler);
				return new EventHandler<TEventArgs>(wrapper.Execute);
			}
		#endregion
	}
}

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Paulo Zemek
Engineer Microsoft Corporation
United States United States
I started to program computers when I was 11 years old, as a hobbist, programming in AMOS Basic and Blitz Basic for Amiga.
At 12 I had my first try with assembler, but it was too difficult at the time. Then, in the same year, I learned C and, after learning C, I was finally able to learn assembler (for Motorola 680x0).
Not sure, but probably between 12 and 13, I started to learn C++. I always programmed "in an object oriented way", but using function pointers instead of virtual methods.
 
At 15 I started to learn Pascal at school and to use Delphi. At 16 I started my first internship (using Delphi). At 18 I started to work professionally using C++ and since then I've developed my programming skills as a professional developer in C++ and C#, generally creating libraries that help other developers do they work easier, faster and with less errors.
 
Now I just started working as a Senior Software Engineer at Microsoft.
 
Want more info or simply want to contact me?
Take a look at: http://paulozemek.azurewebsites.net/
Or e-mail me at: paulozemek@outlook.com
 
Codeproject MVP 2012
Microsoft MVP 2013-2014

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