Click here to Skip to main content
Click here to Skip to main content
Articles » Languages » C# » General » Downloads
 
Add your own
alternative version

Lazy Alternatives - LazyAndWeak and BackgroundLoader

, 1 Dec 2011
This article will present two alternatives to Lazy.
LazyAlternatives.zip
LazyAlternatives
LazyAlternatives.suo
LazyAlternativesSample
Properties
Settings.settings
Pfz
Caching
Collections
DataTypes
DynamicObjects
Internal
Extensions
Factoring
Pfz.csproj.user
Pfz.Phone.csproj.user
Pfz.ruleset
Pfz.Silverlight.csproj.user
Pfz.snk
Pfz.suo
PhoneSpecific
Properties
Remoting
Instructions
Internal
Serializers
Udp
Serialization
BinaryBuiltIn
Threading
Contexts
Disposers
Unsafe
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using Pfz.Caching;
using Pfz.Threading;

namespace Pfz.Collections
{
	/// <summary>
	/// Dictionary that uses a ReaderWriterLock for its accesses (so the call to each method
	/// is thread-safe) and also gets "trimmed" automatically when garbage collections occur.
	/// 
	/// It is also capable of auto-collecting Values that are empty collections and does not 
	/// accept null values (or remove an item set to null).
	/// </summary>
	public class AutoTrimDictionary<TKey, TValue>:
		ReaderWriterSafeDisposable,
		IDictionary<TKey, TValue>,
		IGarbageCollectionAware
	{
		private Dictionary<TKey, TValue> _dictionary = new Dictionary<TKey, TValue>();

		/// <summary>
		/// Creates a new instance of AutoTrimDictionary.
		/// </summary>
		public AutoTrimDictionary()
		{
			GCUtils.RegisterForCollectedNotification(this);
		}

		/// <summary>
		/// Unregisters this dictionary from GCUtils.Collected.
		/// </summary>
		protected override void Dispose(bool disposing)
		{
			if (disposing)
			{
				GCUtils.UnregisterFromCollectedNotification(this);
				_dictionary = null;
			}

			base.Dispose(disposing);
		}
		void IGarbageCollectionAware.OnCollected()
		{
			try
			{
				using(var upgradeableLock = DisposeLock.UpgradeableLock())
				{
					if (WasDisposed)
					{
						GCUtils.UnregisterFromCollectedNotification(this);
						return;
					}

					Dictionary<TKey, TValue> newDictionary;
					if (MustRemoveEmptyCollections)
					{
						var oldDictionary = _dictionary;
						newDictionary = new Dictionary<TKey, TValue>(_dictionary.Count);

						foreach(var pair in oldDictionary)
						{
							var key = pair.Key;
							var value = pair.Value;

							IEnumerable<object> enumerable = value as IEnumerable<object>;
							if (enumerable != null)
								using (var enumerator = enumerable.GetEnumerator())
									if (!enumerator.MoveNext())
										continue;

							newDictionary.Add(key, value);
						}
					}
					else
						newDictionary = new Dictionary<TKey, TValue>(_dictionary);

					upgradeableLock.Upgrade();
					_dictionary = newDictionary;
				}
			}
			catch
			{
			}
		}

		/// <summary>
		/// Gets or sets a value indicating that values that are empty-collections must be removed
		/// during a collection.
		/// </summary>
		public bool MustRemoveEmptyCollections { get; set; }

		/// <summary>
		/// Redirects the call to the real dictionary, in a thread-safe manner.
		/// </summary>
		public void Add(TKey key, TValue value)
		{
			if (value == null)
				throw new ArgumentNullException("value");

			using(DisposeLock.WriteLock())
			{
				CheckUndisposed();

				_dictionary.Add(key, value);
			}
		}

		/// <summary>
		/// Redirects the call to the real dictionary, in a thread-safe manner.
		/// </summary>
		public bool ContainsKey(TKey key)
		{
			using(DisposeLock.ReadLock())
			{
				CheckUndisposed();

				return _dictionary.ContainsKey(key);
			}
		}

		/// <summary>
		/// Redirects the call to the real dictionary, in a thread-safe manner.
		/// </summary>
		public ICollection<TKey> Keys
		{
			get
			{
				using(DisposeLock.ReadLock())
				{
					CheckUndisposed();

					return _dictionary.Keys.ToList();
				}
			}
		}

		/// <summary>
		/// Redirects the call to the real dictionary, in a thread-safe manner.
		/// </summary>
		public bool Remove(TKey key)
		{
			using(DisposeLock.WriteLock())
			{
				CheckUndisposed();

				return _dictionary.Remove(key);
			}
		}

		/// <summary>
		/// Redirects the call to the real dictionary, in a thread-safe manner.
		/// </summary>
		public bool TryGetValue(TKey key, out TValue value)
		{
			using(DisposeLock.ReadLock())
			{
				CheckUndisposed();

				return _dictionary.TryGetValue(key, out value);
			}
		}

		/// <summary>
		/// Redirects the call to the real dictionary, in a thread-safe manner.
		/// </summary>
		public ICollection<TValue> Values
		{
			get
			{
				using(DisposeLock.ReadLock())
				{
					CheckUndisposed();

					return _dictionary.Values.ToList();
				}
			}
		}

		/// <summary>
		/// Redirects the call to the real dictionary, in a thread-safe manner.
		/// </summary>
		public TValue this[TKey key]
		{
			get
			{
				using(DisposeLock.ReadLock())
				{
					CheckUndisposed();

					return _dictionary[key];
				}
			}
			set
			{
				if (value == null)
					throw new ArgumentNullException("value");

				using(DisposeLock.WriteLock())
				{
					CheckUndisposed();

					_dictionary[key] = value;
				}
			}
		}


		void ICollection<KeyValuePair<TKey, TValue>>.Add(KeyValuePair<TKey, TValue> item)
		{
			if (item.Value == null)
				throw new ArgumentException("item.Value can't be null.");

			using(DisposeLock.WriteLock())
			{
				CheckUndisposed();

				_dictionary.Add(item.Key, item.Value);
			}
		}

		/// <summary>
		/// Redirects the call to the real dictionary, in a thread-safe manner.
		/// </summary>
		public void Clear()
		{
			using(DisposeLock.WriteLock())
			{
				CheckUndisposed();

				_dictionary.Clear();
			}
		}

		bool ICollection<KeyValuePair<TKey, TValue>>.Contains(KeyValuePair<TKey, TValue> item)
		{
			using(DisposeLock.ReadLock())
			{
				CheckUndisposed();
					
				ICollection<KeyValuePair<TKey, TValue>> dictionary = _dictionary;
				return dictionary.Contains(item);
			}
		}

		/// <summary>
		/// Redirects the call to the real dictionary, in a thread-safe manner.
		/// </summary>
		public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
		{
			using(DisposeLock.ReadLock())
			{
				CheckUndisposed();

				ICollection<KeyValuePair<TKey, TValue>> dictionary = _dictionary;
				dictionary.CopyTo(array, arrayIndex);
			}
		}

		/// <summary>
		/// Redirects the call to the real dictionary, in a thread-safe manner.
		/// </summary>
		public int Count
		{
			get
			{
				using(DisposeLock.ReadLock())
				{
					CheckUndisposed();

					return _dictionary.Count;
				}
			}
		}

		bool ICollection<KeyValuePair<TKey, TValue>>.IsReadOnly
		{
			get
			{
				return false;
			}
		}

		bool ICollection<KeyValuePair<TKey, TValue>>.Remove(KeyValuePair<TKey, TValue> item)
		{
			using(DisposeLock.WriteLock())
			{
				CheckUndisposed();

				ICollection<KeyValuePair<TKey, TValue>> dictionary = _dictionary;
				return dictionary.Remove(item);
			}
		}

		/// <summary>
		/// Redirects the call to the real dictionary, in a thread-safe manner.
		/// </summary>
		public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
		{
			using(DisposeLock.ReadLock())
			{
				CheckUndisposed();

				return _dictionary.ToList().GetEnumerator();
			}
		}

		IEnumerator IEnumerable.GetEnumerator()
		{
			return GetEnumerator();
		}
	}
}

By viewing downloads associated with this article you agree to the Terms of Service and the article's licence.

If a file you wish to view isn't highlighted, and is a text file (not binary), please let us know and we'll add colourisation support for it.

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

| Advertise | Privacy | Mobile
Web04 | 2.8.140721.1 | Last Updated 1 Dec 2011
Article Copyright 2011 by Paulo Zemek
Everything else Copyright © CodeProject, 1999-2014
Terms of Service
Layout: fixed | fluid