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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;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using Pfz.Extensions.MonitorLockExtensions;
using Pfz.Threading;

namespace Pfz.Caching
{
	/// <summary>
	/// This is a dictionary that allow values to be collected.
	/// </summary>
	[Serializable]
	public class WeakDictionary<TKey, TValue>:
		ThreadSafeDisposable,
		IDictionary<TKey, TValue>,
		ISerializable
	where
		TValue: class
	{
		#region Private dictionary of EquatableWeakReferences
			private volatile Dictionary<TKey, KeepAliveGCHandle> fDictionary = new Dictionary<TKey,KeepAliveGCHandle>();
		#endregion
		
		#region Constructor
			/// <summary>
			/// Creates the dictionary.
			/// </summary>
			public WeakDictionary()
			{
				GCUtils.Collected += p_Collected;
			}
		#endregion
		#region Dispose
			/// <summary>
			/// Frees all handles used to know if an item was collected or not.
			/// </summary>
			protected override void Dispose(bool disposing)
			{
				if (disposing)
					GCUtils.Collected -= p_Collected;
				
				var dictionary = fDictionary;
				if (dictionary != null)
				{
					fDictionary = null;
					
					foreach(KeepAliveGCHandle wr in dictionary.Values)
						wr.Free();
				}
				
				base.Dispose(disposing);
			}
		#endregion
		#region p_Collected
			private void p_Collected()
			{
				try
				{
					DisposeLock.TryLockWithTimeout
					(
						delegate
						{
							if (WasDisposed)
							{
								GCUtils.Collected -= p_Collected;
								return;
							}
								
							var oldDictionary = fDictionary;
							var newDictionary = new Dictionary<TKey, KeepAliveGCHandle>(oldDictionary.Count);
							foreach(var pair in oldDictionary)
							{
								var wr = pair.Value;
								
								if (wr.IsAlive)
									newDictionary.Add(pair.Key, pair.Value);
								else
									wr.Free();
							}
							
							fDictionary = newDictionary;
						}
					);
				}
				catch
				{
				}
			}
		#endregion
		
		#region Properties
			#region Count
				/// <summary>
				/// Gets the number of items in this dictionary.
				/// </summary>
				public int Count
				{
					get
					{
						int result = 0;
						
						DisposeLock.LockWithTimeout
						(
							delegate
							{
								CheckUndisposed();
								
								result = fDictionary.Count;
							}
						);
						
						return result;
					}
				}
			#endregion
			#region this[]
				/// <summary>
				/// Gets or sets a value for the specified key.
				/// Returns null if the item does not exist. The indexer, when
				/// used as an IDictionary throws an exception when the item does
				/// not exist.
				/// </summary>
				public TValue this[TKey key]
				{
					get
					{
						if (key == null)
							throw new ArgumentNullException("key");
					
						TValue result = default(TValue);
						
						DisposeLock.LockWithTimeout
						(
							delegate
							{
								CheckUndisposed();
								
								KeepAliveGCHandle wr;
								if (!fDictionary.TryGetValue(key, out wr))
									return;
								
								result = (TValue)wr.Target;
							}
						);
						
						return result;
					}
					set
					{
						if (key == null)
							throw new ArgumentNullException("key");
					
						DisposeLock.LockWithTimeout
						(
							delegate
							{
								CheckUndisposed();
								
								if (value == null)
									p_Remove(key);
								else
								{
									KeepAliveGCHandle wr;
									
									var dictionary = fDictionary;
									if (dictionary.TryGetValue(key, out wr))
										wr.Target = value;
									else
										p_Add(key, value, dictionary);
								}
							}
						);
					}
				}
			#endregion
			
			#region Keys
				/// <summary>
				/// Gets the Keys that exist in this dictionary.
				/// </summary>
				public ICollection<TKey> Keys
				{
					get
					{
						ICollection<TKey> result = null;
						
						DisposeLock.LockWithTimeout
						(
							delegate
							{
								CheckUndisposed();
								
								result = fDictionary.Keys.ToArray();
							}
						);
						
						return result;
					}
				}
			#endregion
			#region Values
				/// <summary>
				/// Gets the values that exist in this dictionary.
				/// </summary>
				public ICollection<TValue> Values
				{
					get
					{
						ICollection<TValue> baseResult = null;
						
						DisposeLock.LockWithTimeout
						(
							delegate
							{
								CheckUndisposed();
								
								var dictionary = fDictionary;

								List<TValue> result = new List<TValue>();
								foreach(KeepAliveGCHandle wr in dictionary.Values)
								{
									TValue item = (TValue)wr.TargetAllowingExpiration;
									if (item != null)
										result.Add(item);
								}
								
								baseResult = result;
							}
						);
						
						return baseResult;
					}
				}
			#endregion
		#endregion
		#region Methods
			#region Clear
				/// <summary>
				/// Clears all items in this dictionary.
				/// </summary>
				public void Clear()
				{
					DisposeLock.LockWithTimeout
					(
						delegate
						{
							CheckUndisposed();
							
							var dictionary = fDictionary;
							foreach(KeepAliveGCHandle wr in dictionary.Values)
								wr.Free();
								
							dictionary.Clear();
						}
					);
				}
			#endregion
			#region Add
				/// <summary>
				/// Adds an item to this dictionary. Throws an exception if an item
				/// with the same key already exists.
				/// </summary>
				public void Add(TKey key, TValue value)
				{
					if (key == null)
						throw new ArgumentNullException("key");
						
					if (value == null)
						throw new ArgumentNullException("value");
						
					DisposeLock.LockWithTimeout
					(
						delegate
						{
							CheckUndisposed();
							
							var dictionary = fDictionary;
							KeepAliveGCHandle wr;
							if (dictionary.TryGetValue(key, out wr))
							{
								if (wr.IsAlive)
									throw new ArgumentException("An element with the same key \"" + key + "\" already exists.");
								
								wr.Target = value;
							}
							else
								p_Add(key, value, dictionary);
						}
					);
				}
			#endregion
			#region Remove
				/// <summary>
				/// Removes an item with the given key from the dictionary.
				/// </summary>
				public bool Remove(TKey key)
				{
					if (key == null)
						throw new ArgumentNullException("key");
					
					bool result = false;
					
					DisposeLock.LockWithTimeout
					(
						delegate
						{
							CheckUndisposed();

							result = p_Remove(key);
						}
					);
					
					return result;
				}
			#endregion
			
			#region ContainsKey
				/// <summary>
				/// Gets a value indicating if an item with the specified key exists.
				/// </summary>
				public bool ContainsKey(TKey key)
				{
					return fDictionary.ContainsKey(key);
				}
			#endregion
			
			#region GetEnumerator
				/// <summary>
				/// Gets an enumerator with all key/value pairs that exist in
				/// this dictionary.
				/// </summary>
				public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
				{
					return ToList().GetEnumerator();
				}
			#endregion
			#region ToList
				/// <summary>
				/// Gets a list with all non-collected key/value pairs.
				/// </summary>
				public List<KeyValuePair<TKey, TValue>> ToList()
				{
					List<KeyValuePair<TKey, TValue>> result = new List<KeyValuePair<TKey, TValue>>();
					
					DisposeLock.LockWithTimeout
					(
						delegate
						{
							CheckUndisposed();
							
							var dictionary = fDictionary;
							foreach(var pair in dictionary)
							{
								TValue target = (TValue)pair.Value.TargetAllowingExpiration;
								if (target != null)
									result.Add(new KeyValuePair<TKey, TValue>(pair.Key, target));
							}
						}
					);
					
					return result;
				}
			#endregion
			
			#region p_Add
				private static void p_Add(TKey key, TValue value, Dictionary<TKey, KeepAliveGCHandle> dictionary)
				{
					try
					{
					}
					finally
					{
						KeepAliveGCHandle wr = new KeepAliveGCHandle(value);
						try
						{
							dictionary.Add(key, wr);
						}
						catch
						{
							wr.Free();
							throw;
						}
					}
				}
			#endregion
			#region p_Remove
				private bool p_Remove(TKey key)
				{
					var dictionary = fDictionary;
					KeepAliveGCHandle wr;
					if (!dictionary.TryGetValue(key, out wr))
						return false;

					wr.Free();
					return dictionary.Remove(key);
				}
			#endregion
		#endregion
		#region Interfaces
			#region IDictionary<TKey,TValue> Members
				bool IDictionary<TKey, TValue>.TryGetValue(TKey key, out TValue value)
				{
					value = this[key];
					return value != null;
				}
				TValue IDictionary<TKey, TValue>.this[TKey key]
				{
					get
					{
						TValue result = this[key];
						if (result == null)
							throw new KeyNotFoundException("The given key \"" + key + "\" was not found in the dictionary.");
						
						return result;
					}
					set
					{
						this[key] = value;
					}
				}
			#endregion
			#region ICollection<KeyValuePair<TKey,TValue>> Members
				void ICollection<KeyValuePair<TKey, TValue>>.Add(KeyValuePair<TKey, TValue> item)
				{
					Add(item.Key, item.Value);
				}
				bool ICollection<KeyValuePair<TKey, TValue>>.Contains(KeyValuePair<TKey, TValue> item)
				{
					if (item.Value == null)
						return false;
				
					KeepAliveGCHandle wr;
					if (!fDictionary.TryGetValue(item.Key, out wr))
						return false;
					
					return object.Equals(wr.TargetAllowingExpiration, item.Value);
				}
				void ICollection<KeyValuePair<TKey, TValue>>.CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
				{
					ToList().CopyTo(array, arrayIndex);
				}
				bool ICollection<KeyValuePair<TKey, TValue>>.IsReadOnly
				{
					get
					{
						return false;
					}
				}
				bool ICollection<KeyValuePair<TKey, TValue>>.Remove(KeyValuePair<TKey, TValue> item)
				{
					if (item.Value == null)
						return false;
				
					bool result = false;
					
					DisposeLock.LockWithTimeout
					(
						delegate
						{
							CheckUndisposed();
							
							KeepAliveGCHandle wr;
							var dictionary = fDictionary;
							if (!dictionary.TryGetValue(item.Key, out wr))
								return;
							
							if (!object.Equals(wr.TargetAllowingExpiration, item.Value))
								return;

							result = p_Remove(item.Key);
						}
					);
					
					return result;
				}
			#endregion
			#region IEnumerable Members
				IEnumerator IEnumerable.GetEnumerator()
				{
					return GetEnumerator();
				}
			#endregion

			#region ISerializable Members
				/// <summary>
				/// Creates the dictionary from serialization info.
				/// Actually, it does not load anything, as if everything was
				/// collected.
				/// </summary>
				protected WeakDictionary(SerializationInfo info, StreamingContext context):
					this()
				{
				}
				/// <summary>
				/// It is here to be inherited. Actually, this does not
				/// add anything, as if everything was collected.
				/// </summary>
				protected virtual void GetObjectData(SerializationInfo info, StreamingContext context)
				{
				}
				void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
				{
					DisposeLock.LockWithTimeout
					(
						delegate
						{
							CheckUndisposed();
							
							GetObjectData(info, context);
						}
					);
				}
			#endregion
		#endregion
	}
}

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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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