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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.Runtime.InteropServices;
using Pfz.DataTypes;

namespace Pfz.Caching
{
	/// <summary>
	/// This is the struct that implements the code for ThreadUnsafeReference and
	/// Reference.
	/// </summary>
	public struct ThreadUnsafeReferenceSlim<T>:
		IReference<T>,
		IEquatable<IReference<T>>,
		#if !SILVERLIGHT
			ICloneable<ThreadUnsafeReferenceSlim<T>>,
		#endif
		IDisposable
	where
		T: class
	{
		private object _obj;
		private GCHandleType _handleType;

		/// <summary>
		/// Creates a new reference using the given value and handle type.
		/// </summary>
		public ThreadUnsafeReferenceSlim(T value, GCHandleType handleType)
		{
			_handleType = handleType;

			switch(handleType)
			{
				case GCHandleType.Normal:
					_obj = value;
					break;

				case GCHandleType.Weak:
					_obj = new WeakReference(value);
					break;

				default:
					throw new ArgumentException();
			}
		}

		/// <summary>
		/// Frees the handle immediatelly.
		/// </summary>
		public void Dispose()
		{
			_obj = null;
		}
		
		/// <summary>
		/// Gets or sets the value pointed by the handle.
		/// </summary>
		public T Value
		{
			get
			{
				var obj = _obj;
				if (obj == null)
					return null;

				WeakReference wr = obj as WeakReference;
				if (wr != null)
					return (T)wr.Target;

				return (T)obj;
			}
			set
			{
				if (_handleType == GCHandleType.Weak)
					_obj = new WeakReference(value);
				else
					_obj = value;
			}
		}
		
		/// <summary>
		/// Gets or sets the handle type.
		/// </summary>
		public GCHandleType HandleType
		{
			get
			{
				return _handleType;
			}
			set
			{
				if (value == _handleType)
					return;
				
				switch(value)
				{
					case GCHandleType.Normal:
						_obj = Value;
						break;

					case GCHandleType.Weak:
						_obj = new WeakReference(Value);
						break;

					default:
						throw new ArgumentException();
				}

				_handleType = value;
			}
		}

		/// <summary>
		/// Gets the data of this Reference.
		/// </summary>
		public ReferenceData<T> GetData()
		{
			return new ReferenceData<T>(Value, _handleType);
		}

		/// <summary>
		/// Sets the data of this reference.
		/// </summary>
		public void Set(GCHandleType handleType, T value)
		{
			switch(handleType)
			{
				case GCHandleType.Normal:
					_obj = value;
					break;

				case GCHandleType.Weak:
					_obj = new WeakReference(value);
					break;

				default:
					throw new ArgumentException();
			}

			_handleType = handleType;
		}

		/// <summary>
		/// Gets the HashCode of the Value.
		/// </summary>
		public override int GetHashCode()
		{
			var value = Value;
			if (value == null)
				return 0;

			return value.GetHashCode();
		}

		/// <summary>
		/// Compares the Value of this reference with the value of another reference.
		/// </summary>
		public override bool Equals(object obj)
		{
			var other = obj as IReference<T>;
			if (other != null)
				return Equals(other);

			return false;
		}

		/// <summary>
		/// Compares the Value of this reference with the value of another reference.
		/// </summary>
		public bool Equals(IReference<T> other)
		{
			if (other == null)
				return false;

			return Value == other.Value;
		}
		
		#region IValueContainer Members
			object IValueContainer.Value
			{
				get
				{
					return Value;
				}
				set
				{
					Value = (T)value;
				}
			}
		#endregion
		#region ICloneable<ThreadUnsafeReference<T>> Members
			/// <summary>
			/// Creates a copy of this reference.
			/// </summary>
			public ThreadUnsafeReferenceSlim<T> Clone()
			{
				return new ThreadUnsafeReferenceSlim<T>(Value, _handleType);
			}
		#endregion
		#region ICloneable Members
			#if !SILVERLIGHT
			object ICloneable.Clone()
			{
				return Clone();
			}
			#endif
		#endregion
		#region IReference Members
			void IReference.Set(GCHandleType handleType, object value)
			{
				Set(handleType, (T)value);
			}
			IReferenceData IReference.GetData()
			{
				return GetData();
			}
		#endregion
	}
}

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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
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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