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WPF Control Factory

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20 Apr 2010CPOL6 min read 37.5K   418   16  
This article explains some advantages and disadvantages of factories, and shows one to use for generating WPF Controls.
using System;
using Pfz.Extensions.DisposeExtensions;
using Pfz.Extensions.MonitorLockExtensions;

namespace Pfz.Threading
{
	/// <summary>
	/// This class is useful if you need to implement the dispose pattern
	/// in a thread-safe manner.
	/// It guarantees that dispose will be called only once, even if many 
	/// threads try to call Dispose at once. In your code, you must lock 
	/// DisposeLock, check if the object is disposed and call anything that 
	/// must be guaranteed to run before dispose inside the lock block.
	/// </summary>
	public abstract class ThreadSafeDisposable:
		IAdvancedDisposable
	{
		#region Destructor
			/// <summary>
			/// Calls Dispose(false);
			/// </summary>
			~ThreadSafeDisposable()
			{
				Dispose(false);
			}
		#endregion
		#region Dispose
			#region Without parameters
				/// <summary>
				/// Calls Dispose(true) to release all resources.
				/// Guarantees that only a single call to Dispose(true) is done 
				/// even if  this method is invoked multiple times or by many 
				/// different threads at the same time.
				/// </summary>
				public void Dispose()
				{
					IDisposable disposer = null;
					try
					{
						AbortSafe.Run(() => disposer = fDisposeLock.LockWithTimeout());

						if (fWasDisposed)
							return;
						
						try
						{
						}
						finally
						{
							fWasDisposed = true;
							
							disposer.Dispose();
							
							Dispose(true);
							GC.SuppressFinalize(this);
						}
					}
					finally
					{
						disposer.CheckedDispose();
					}
				}
			#endregion
			#region Protected - bool disposing
				/// <summary>
				/// Implement this method to release all resources used by this object.
				/// </summary>
				/// <param name="disposing">
				/// This parameter is true if it was called by a user call to Dispose(),
				/// and false if it was called by a destructor. If false, you don't need
				/// to release managed resources (in general, you don't need to set any
				/// variables to null or even reference other objects, only freeing 
				/// "unsafe" pointers).
				/// </param>
				protected virtual void Dispose(bool disposing)
				{
				}
			#endregion
		#endregion
		
		#region Properties
			#region WasDisposed
				private volatile bool fWasDisposed;
				
				/// <summary>
				/// Returns true if a call to Dispose was already done (or still in
				/// progress in another thread). If it is true, you can't continue
				/// to use your object.
				/// </summary>
				public bool WasDisposed
				{
					get
					{
						return fWasDisposed;
					}
				}
			#endregion
			#region DisposeLock
				private volatile object fDisposeLock = new object();
				
				/// <summary>
				/// This is the lock used during dispose. You may want to lock
				/// some of your code against dispose using this lock.
				/// The preferred way to use it is: AbortSafe.Lock
				/// (
				///		DisposeLock,
				///		delegate
				///		{
				///			CheckUndisposed();
				///		
				///			... your protected code here ...
				///		}
				///	);
				/// </summary>
				public object DisposeLock
				{
					get
					{
						return fDisposeLock;
					}
				}
			#endregion
		#endregion
		#region Methods
			#region CheckUndisposed
				/// <summary>
				/// Checks if the objects is disposed. If it is, throws an 
				/// ObjectDisposedException. Call this as the first method inside a 
				/// AbortSafe.Lock
				/// (
				///		DisposeLock,
				///		delegate
				///		{
				///			CheckUndisposed(); 
				///			... your protected code here ...
				///		}
				///	);
				/// 
				/// or simple call it without any lock if you only want to throw
				/// an exception if the object is already disposed but such a call
				/// is read-only.
				/// </summary>
				public void CheckUndisposed()
				{
					if (fWasDisposed)
						throw new ObjectDisposedException(GetType().FullName);
				}
			#endregion
		#endregion
	}
}

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


Written By
Software Developer (Senior) Microsoft
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.

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 (in October 2014 I started working at Microsoft, so I can't be a Microsoft MVP anymore).

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