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WPF Control Factory

, 20 Apr 2010
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.Generic;
using System.Threading;
using Pfz.Caching;
using Pfz.Extensions.MonitorLockExtensions;

namespace Pfz.Threading
{
	/// <summary>
	/// This is a thread pool that, different from System.Threading.ThreadPool,
	/// does not have a thread limit and the threads are not background while
	/// they run. Comparing to the system ThreadPool, it is better if the
	/// thread can enter in wait mode. This happens when one thread has a 
	/// "fast" process, but can only terminate after another thread returns.
	/// 
	/// This thread pool keep threads alive for a certain number of generations.
	/// The default value is two. So, at the first use, it lives for one more
	/// generation. After the second use in that generation, it is marked to 
	/// live for two generations. Subsequent uses in this generation will not
	/// change anything. Do not use very high values, as this can cause memory
	/// usage problems.
	/// </summary>
	public static class UnlimitedThreadPool
	{
		#region Private fields
			private static object fLock = new object();
			private static volatile List<Parameters> fFreeEvents = new List<Parameters>();
		#endregion
		
		#region Constructor
			static UnlimitedThreadPool()
			{
				GCUtils.Collected += p_Collected;
			}
		#endregion
		#region p_Collected
			private static void p_Collected()
			{
				try
				{
					int minimumCollectionNumber = GC.CollectionCount(GC.MaxGeneration);
					List<Parameters> freeEvents;
					AbortSafe.UnabortableLock
					(
						fLock,
						delegate
						{
							freeEvents = fFreeEvents;
							
							var newFreeEvents = new List<Parameters>();
							foreach(Parameters p in freeEvents)
							{
								if (p.KeepAliveUntilCollectionOfNumber >= minimumCollectionNumber)
									newFreeEvents.Add(p);
								else
								{
									p.Action = null;
									p.WaitEvent.Set();
								}
							}
							fFreeEvents = newFreeEvents;
						}
					);
				}
				catch
				{
				}
			}
		#endregion
		
		#region Properties
			#region CollectionsToKeepAlive
				private static volatile int fCollectionsToKeepAlive = 2;
				
				/// <summary>
				/// Gets or sets the maximum number of collections to keep a Thread from this pool
				/// alive. The default value is two.
				/// </summary>
				public static int CollectionsToKeepAlive
				{
					get
					{
						return fCollectionsToKeepAlive;
					}
					set
					{
						if (value <= 0)
							throw new ArgumentException("value must be greater than zero.", "UnlimitedThreadPool.CollectionsToKeepAlive");
							
						fCollectionsToKeepAlive = value;
					}
				}
			#endregion
		#endregion
		#region Methods
			#region Run
				/// <summary>
				/// Runs an action in another thread. Uses an existing thread if one is 
				/// available or creates a new one if none are available, so this call will
				/// not hang if there are no available threads.
				/// </summary>
				/// <param name="action">The function to execute.</param>
				public static void Run(Action action)
				{
					Run
					(
						delegate(object obj)
						{
							action();
						},
						null
					);
				}
				
				/// <summary>
				/// Runs an action in another thread. Uses an existing thread if one is 
				/// available or creates a new one if none are available, so this call will
				/// not hang if there are no available threads.
				/// </summary>
				/// <param name="action">The function to execute.</param>
				/// <param name="parameter">The object passed as parameter to the action.</param>
				public static void Run(Action<object> action, object parameter)
				{
					if (action == null)
						throw new ArgumentNullException("action");
				
					Parameters p = null;
					fLock.LockWithTimeout
					(
						delegate
						{
							int count = fFreeEvents.Count;
							if (count > 0)
							{
								int index = count - 1;
								p = fFreeEvents[index];
								fFreeEvents.RemoveAt(index);
							}
						}
					);
							
					if (p == null)
					{
						p = new Parameters();
						p.WaitEvent = new ManualResetEvent(false);
						Thread thread = new Thread(p_RunThread);
						p.Thread = thread;
						thread.Start(p);
					}

					p.Action = action;
					p.Parameter = parameter;
					
					p.Thread.IsBackground = false;
					p.WaitEvent.Set();
				}
				
				/// <summary>
				/// Runs an action in another thread. Uses an existing thread if one is 
				/// available or creates a new one if none are available, so this call will
				/// not hang if there are no available threads.
				/// </summary>
				/// <typeparam name="T">The type of the parameter.</typeparam>
				/// <param name="action">The function to execute.</param>
				/// <param name="parameter">The object passed as parameter to the action.</param>
				public static void Run<T>(Action<T> action, T parameter)
				{
					Run
					(
						delegate(object obj)
						{
							T typedParameter = (T)obj;
							action(typedParameter);
						},
						parameter
					);
				}
			#endregion
			
			#region p_RunThread
				private static void p_RunThread(object parameters)
				{
					Thread currentThread = Thread.CurrentThread;
					Parameters p = (Parameters)parameters;
					ManualResetEvent waitEvent = p.WaitEvent;
					
					try
					{
						while(true)
						{
							waitEvent.WaitOne();
							
							if (p.Action == null)
							{
								waitEvent.Close();
								return;
							}
							
							p.Action(p.Parameter);

							fLock.LockWithTimeout
							(
								delegate
								{
									int actualCollectionNumber = GC.CollectionCount(GC.MaxGeneration);
									int keepAliveUntil = p.KeepAliveUntilCollectionOfNumber;
									
									if (keepAliveUntil <= actualCollectionNumber)
										p.KeepAliveUntilCollectionOfNumber = actualCollectionNumber + 1;
									else
									{
										int maxValue = actualCollectionNumber + fCollectionsToKeepAlive;
										if (keepAliveUntil < maxValue)
											p.KeepAliveUntilCollectionOfNumber = keepAliveUntil + 1;
									}

									currentThread.IsBackground = true;
									waitEvent.Reset();
									fFreeEvents.Add(p);
								}
							);
						}
					}
					finally
					{
						if (currentThread.IsBackground)
						{
							fLock.LockWithTimeout
							(
								() => fFreeEvents.Remove(p)
							);
						}
					}
				}
			#endregion
		#endregion

		#region Parameters - Nested class
			private sealed class Parameters
			{
				internal Thread Thread;
				internal ManualResetEvent WaitEvent;
				internal volatile Action<object> Action;
				internal volatile object Parameter;
				internal volatile int KeepAliveUntilCollectionOfNumber;
			}
		#endregion
	}
}

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License

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

About the Author

Paulo Zemek
Architect
Canada Canada
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.
 
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

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