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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
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
WpfControlFactorySample.suo
using System;
using System.Runtime.Serialization;

namespace Pfz.Caching
{
	/// <summary>
	/// This is a WeakReference class with KeepAlive capability.
	/// Everytime you get the Target from this WeakReference, it calls the GCUtils.KeepAlive.
	/// This is a very simple way to use weak-references only to your objects and also
	/// keep them alive if they are used frequently.
	/// </summary>
	[Serializable]
	public class KeepAliveWeakReference:
		WeakReference
	{
		#region Constructors
			/// <summary>
			/// Constructs a KeepAliveWeakReference pointing to a target.
			/// </summary>
			/// <param name="target">The target of this KeepAliveWeakReference.</param>
			public KeepAliveWeakReference(object target):
				base(target)
			{
				GCUtils.KeepAlive(target);
			}
			
			/// <summary>
			/// Constructs a KeepAliveWeakReference pointing to a target and allowing to trackResurrection.
			/// The Caching framework does not use this constructor, it is only here to keep the functionality
			/// of the second parameter present in the System.WeakReference constructor.
			/// </summary>
			/// <param name="target">The target of this WeakReference.</param>
			/// <param name="trackResurrection">Boolean indicating if this WeakReference must trackResurrection.</param>
			public KeepAliveWeakReference(object target, bool trackResurrection):
				base(target, trackResurrection)
			{
				GCUtils.KeepAlive(target);
			}
			
			/// <summary>
			/// Constructs a KeepAliveWeakReference pointing to a target, allowing to trackResurrection and
			/// allowing you to tell if immediateExpiration is allowed. The other two constructors always
			/// do a KeepAlive, so they don't allow immediateExpiration.
			/// </summary>
			/// <param name="target">The target of this WeakReference.</param>
			/// <param name="trackResurrection">Boolean indicating if this WeakReference must trackResurrection.</param>
			/// <param name="allowImmediateExpiration">
			/// If true, the target can be collected in the next collection.
			/// If false, it will be kept alive at the next collection.
			/// </param>
			public KeepAliveWeakReference(object target, bool trackResurrection, bool allowImmediateExpiration):
				base(target, trackResurrection)
			{
				if (!allowImmediateExpiration)
					GCUtils.KeepAlive(target);
			}
			
			/// <summary>
			/// Simple keeping the serialization constructor present in WeakReference.
			/// </summary>
			/// <param name="info"></param>
			/// <param name="context"></param>
			protected KeepAliveWeakReference(SerializationInfo info, StreamingContext context):
				base(info, context)
			{
			}
		#endregion
		
		#region Target
			/// <summary>
			/// Overrides the WeakReference.Target, so it calls KeepAlive while gets or sets the Target.
			/// </summary>
			public override object Target
			{
				get
				{
					object result = base.Target;
					GCUtils.KeepAlive(result);
					return result;
				}
				set
				{
					GCUtils.Expire(base.Target);
					base.Target = value;
					GCUtils.KeepAlive(value);
				}
			}
		#endregion
		#region TargetAllowingExpiration
			/// <summary>
			/// This is equivalent to a custom WeakReference target, as it's gets or sets the target
			/// without calling KeepAlive. Keep in mind that when an external code uses WeakReference,
			/// you can pass a KeepAliveWeakReference as a parameter, and the conventional Target that
			/// is used by default will have the KeepAlive effect.
			/// </summary>
			public object TargetAllowingExpiration
			{
				get
				{
					return base.Target;
				}
				set
				{
					base.Target = value;
				}
			}
		#endregion
	}
	
	/// <summary>
	/// A typed version of weak-reference.
	/// Note that it simple hides the untyped Target and TargetAllowingExpiration.
	/// If you cast this object as a simple WeakReference you can still set
	/// an invalid typed target to it. This is only a helper class to avoid
	/// manual casts.
	/// </summary>
	/// <typeparam name="T">The type of the objects used by this weak-reference.</typeparam>
	public sealed class KeepAliveWeakReference<T>:
		KeepAliveWeakReference
	where
		T: class
	{
		#region Constructors
			/// <summary>
			/// Constructs a KeepAliveWeakReference pointing to a target.
			/// </summary>
			/// <param name="target">The target of this KeepAliveWeakReference.</param>
			public KeepAliveWeakReference(object target):
				base(target)
			{
			}
			
			/// <summary>
			/// Constructs a KeepAliveWeakReference pointing to a target and allowing to trackResurrection.
			/// The Caching framework does not use this constructor, it is only here to keep the functionality
			/// of the second parameter present in the System.WeakReference constructor.
			/// </summary>
			/// <param name="target">The target of this WeakReference.</param>
			/// <param name="trackResurrection">Boolean indicating if this WeakReference must trackResurrection.</param>
			public KeepAliveWeakReference(object target, bool trackResurrection):
				base(target, trackResurrection)
			{
			}
			
			/// <summary>
			/// Constructs a KeepAliveWeakReference pointing to a target, allowing to trackResurrection and
			/// allowing you to tell if immediateExpiration is allowed. The other two constructors always
			/// do a KeepAlive, so they don't allow immediateExpiration.
			/// </summary>
			/// <param name="target">The target of this WeakReference.</param>
			/// <param name="trackResurrection">Boolean indicating if this WeakReference must trackResurrection.</param>
			/// <param name="allowImmediateExpiration">
			/// If true, the target can be collected in the next collection.
			/// If false, it will be kept alive at the next collection.
			/// </param>
			public KeepAliveWeakReference(object target, bool trackResurrection, bool allowImmediateExpiration):
				base(target, trackResurrection, allowImmediateExpiration)
			{
			}
			
			/// <summary>
			/// Simple keeping the serialization constructor present in WeakReference.
			/// </summary>
			/// <param name="info"></param>
			/// <param name="context"></param>
			private KeepAliveWeakReference(SerializationInfo info, StreamingContext context):
				base(info, context)
			{
			}
		#endregion
		
		#region Target
			/// <summary>
			/// Gets or sets the typed target, calling GCUtils.KeepAlive() 
			/// while doing it.
			/// </summary>
			public new T Target
			{
				get
				{
					return base.Target as T;
				}
				set
				{
					base.Target = value;
				}
			}
		#endregion
		#region TargetAllowingExpiration
			/// <summary>
			/// Gets or sets the typed-target, without calling GCUtils.KeepAlive().
			/// </summary>
			public new T TargetAllowingExpiration
			{
				get
				{
					return base.TargetAllowingExpiration as T;
				}
				set
				{
					base.TargetAllowingExpiration = value;
				}
			}
		#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 hobbyist, 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 their 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, 2015 & 2016
Microsoft MVP 2013-2014 (now I work at Microsoft so I can't be a Microsoft MVP anymore)

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