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WPF Control Factory

, 20 Apr 2010 CPOL 19.2K 292 16
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;
using System.Collections;
using System.Collections.Generic;
using Pfz.Caching;
using Pfz.Threading;

namespace Pfz.Collections
{
	/// <summary>
	/// This class is responsible for distributing a single enumerator
	/// among many enumerator readers, considering such readers can
	/// "loose" some of the items.
	/// This is useful for senting, for example, web-cam frames. A high-speed
	/// client can receive all frames, while a slow client can receive frame
	/// 1, then frame 6, frame 12... but will still receive the "most recent"
	/// frames.
	/// You can inherit this class the the MultiClientEnumerator themselves
	/// if you must only send the difference between frames.
	/// </summary>
	/// <typeparam name="T">
	/// The type of the item that the original enumerator returns.
	/// </typeparam>
	public class EnumeratorDistributor<T>:
		ThreadSafeExceptionAwareDisposable
	where
		T: class
	{
		internal HashSet<EnumeratorDistributorClient<T>> fClientEnumerators = new HashSet<EnumeratorDistributorClient<T>>();
	
		/// <summary>
		/// Creates a new Distributor over the given real enumerator.
		/// </summary>
		public EnumeratorDistributor(IFastEnumerator<T> baseEnumerator)
		{
			if (baseEnumerator == null)
				throw new ArgumentNullException("baseEnumerator");
			
			GCUtils.Collected += p_Collected;
			BaseEnumerator = baseEnumerator;
			
			UnlimitedThreadPool.Run(p_KeepReading);
		}
		
		/// <summary>
		/// Disposes the base enumerator and the clients actually connected.
		/// </summary>
		protected override void Dispose(bool disposing)
		{
			if (disposing)
			{
				GCUtils.Collected -= p_Collected;
			
				var baseEnumerator = BaseEnumerator;
				if (baseEnumerator != null)
				{
					BaseEnumerator = null;
					baseEnumerator.Dispose();
				}
				
				fActualValue = null;
				
				var clients = fClientEnumerators;
				if(clients != null)
				{
					fClientEnumerators = null;

					// the normal lock can be used here, as our dispose is unabortable.
					lock(DisposeLock)
						foreach(var client in clients)
							client.Dispose();
				}
				
				var disposedEvent = Disposed;
				if (disposedEvent != null)
					disposedEvent(this, EventArgs.Empty);
			}
			
			base.Dispose(disposing);
		}
		private void p_Collected()
		{
			var clients = fClientEnumerators;
			if (clients == null)
			{
				GCUtils.Collected -= p_Collected;
				return;
			}
			
			AbortSafe.UnabortableLock
			(
				clients,
				delegate
				{
					// the if is here because there is a bug with trimexcess in empty hashsets, 
					// as the next foreach will throw an exception. 
					// This bug is already reported and should be corrected in future versions.
					if (clients.Count > 0) 
						clients.TrimExcess();
				}
			);
		}
		
		/// <summary>
		/// Gets the BaseEnumerator used by this distributor.
		/// </summary>
		public IFastEnumerator<T> BaseEnumerator { get; private set; }
		
		/// <summary>
		/// Called when this object is disposed.
		/// </summary>
		public event EventHandler Disposed;
		
		private volatile T fActualValue;
		
		/// <summary>
		/// Gets the Actual value without waiting.
		/// </summary>
		public T ActualValue
		{
			get
			{
				return fActualValue;
			}
		}
		
		private void p_KeepReading()
		{
			try
			{
				var baseEnumerator = BaseEnumerator;
				while(true)
				{
					if (WasDisposed)
						return;
					
					var actualValue = baseEnumerator.GetNext();
					fActualValue = actualValue;
					
					AbortSafe.Lock
					(
						DisposeLock,
						delegate
						{
							foreach(var client in fClientEnumerators)
								client.fEvent.Set();
						}
					);
							
					if (actualValue == null)
					{
						Dispose();
						return;
					}
				}
			}
			catch(Exception exception)
			{
				if (!WasDisposed)
					Dispose(exception);
			}
		}
		
		/// <summary>
		/// Creates a client for this enumerator.
		/// Inheritors can initialize additional information before returning 
		/// the enumerator client to you.
		/// </summary>
		public virtual EnumeratorDistributorClient<T> CreateClient()
		{
			return new EnumeratorDistributorClient<T>(this);
		}
	}
}

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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, 2015
Microsoft MVP 2013-2014

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