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Lazy Alternatives - LazyAndWeak and BackgroundLoader

, 1 Dec 2011 CPOL
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.Generic;
using System.Diagnostics.CodeAnalysis;
using Pfz.Extensions;

namespace Pfz.Factoring
{
	/// <summary>
	/// This class is a special dictionary for types, which can also 
	/// search values that are set for base types or interfaces.
	/// </summary>
	public sealed class TypeDictionary<TValue>
	{
		private Dictionary<Type, TValue> _exactTypes = new Dictionary<Type, TValue>();
		private Dictionary<Type, TValue> _inheritedTypes = new Dictionary<Type, TValue>();
		private Dictionary<Type, TValue> _interfaceTypes = new Dictionary<Type, TValue>();
		private Dictionary<Type, TValue> _exactGenericTypes = new Dictionary<Type, TValue>();
		private Dictionary<Type, TValue> _inheritedGenericTypes = new Dictionary<Type, TValue>();
		private Dictionary<Type, TValue> _genericInterfaceTypes = new Dictionary<Type, TValue>();
		
		/// <summary>
		/// Gets a value for a type, without doing a "search".
		/// </summary>
		public TValue this[Type type]
		{
			get
			{
				if (type == null)
					throw new ArgumentNullException("type");

				TValue result;
				
				if (type.IsGenericTypeDefinition)
				{
					if (_exactGenericTypes.TryGetValue(type, out result))
						return result;
						
					if (type.IsInterface)
						return _genericInterfaceTypes[type];
					
					return _inheritedGenericTypes[type];
				}

				if (_exactTypes.TryGetValue(type, out result))
					return result;

				if (type.IsInterface)
					return _interfaceTypes[type];

				return _inheritedTypes[type];
			}
		}
		
		/// <summary>
		/// Clears all items in this dictionary.
		/// </summary>
		public void Clear()
		{
			_exactTypes.Clear();
			_inheritedTypes.Clear();
			_interfaceTypes.Clear();
			_exactGenericTypes.Clear();
			_inheritedGenericTypes.Clear();
			_genericInterfaceTypes.Clear();
		}
		
		/// <summary>
		/// Removes a value for a type.
		/// </summary>
		public bool Remove(Type type)
		{
			if (type == null)
				throw new ArgumentNullException("type");
		
			if (type.IsGenericTypeDefinition)
			{
				if (_exactGenericTypes.Remove(type))
					return true;
				
				if (type.IsInterface)
					return _genericInterfaceTypes.Remove(type);
					
				return _inheritedGenericTypes.Remove(type);
			}
			
			if (_exactTypes.Remove(type))
				return true;
			
			if (type.IsInterface)
				return _interfaceTypes.Remove(type);
			
			return _inheritedTypes.Remove(type);
		}
		
		/// <summary>
		/// Sets a value for the given type.
		/// Register is as exact match or not by the boolean value.
		/// </summary>
		public void Set(Type type, TValue value, bool isInheritable)
		{
			if (isInheritable)
				SetAsInheritable(type, value);
			else
				SetAsExactMatch(type, value);
		}
		
		/// <summary>
		/// Set the value for a given type, but consider the type only as exact match,
		/// so it will not be found as a base type in FindUp.
		/// </summary>
		public void SetAsExactMatch(Type type, TValue value)
		{
			if (type == null)
				throw new ArgumentNullException("type");
				
			if (type.IsGenericTypeDefinition)
				_exactGenericTypes[type] = value;
			else
				_exactTypes[type] = value;
		}
		
		/// <summary>
		/// Sets the value for a given type, and tells that such value can be
		/// used by sub-types if one more appropriate is not found.
		/// </summary>
		public void SetAsInheritable(Type type, TValue value)
		{
			if (type == null)
				throw new ArgumentNullException("type");
			
			if (type.IsGenericTypeDefinition)
			{
				//if (type.IsSealed)
				//	fExactGenericTypes[type] = value;
				//else
				// even if this type is sealed, it must not be used as exact,
				// as something registered for List<> can also work with List<string>,
				// by default.
				
				if (type.IsInterface)
					_genericInterfaceTypes[type] = value;
				else
					_inheritedGenericTypes[type] = value;
			}
			else
			{
				if (type.IsSealed)
					_exactTypes[type] = value;
				else
				if (type.IsInterface)
					_interfaceTypes[type] = value;
				else
					_inheritedTypes[type] = value;
			}
		}
		
		/// <summary>
		/// Finds a value for the actual type or for a parent type.
		/// Returns the default value if nothing is found.
		/// </summary>
		public TValue FindUpOrDefault(Type type)
		{
			TValue result;
			TryFindUp(type, out result);
			return result;
		}
		
		/// <summary>
		/// Tries to find the value for the actual type or for a parent type.
		/// Returns true if the value is found, false otherwise.
		/// </summary>
		[SuppressMessage("Microsoft.Maintainability", "CA1502:AvoidExcessiveComplexity")]
		public bool TryFindUp(Type type, out TValue value)
		{
			if (type == null)
				throw new ArgumentNullException("type");
		
			if (type.IsGenericTypeDefinition)
			{
				if (_exactGenericTypes.TryGetValue(type, out value))
					return true;
			}
			else
			{
				if (_exactTypes.TryGetValue(type, out value))
					return true;

				if (type.IsGenericType)
				{
					// For example, here we can have the List<string> type.
					// But, before searching for a registered type for List<>
					// We need to check if we don't have such type registered in
					// the inheritance dictionary.
				
					if (type.IsInterface)
					{
						if (_interfaceTypes.TryGetValue(type, out value))
							return true;
					}
					else
					{
						if (_inheritedTypes.TryGetValue(type, out value))
							return true;
					}

					Type typeDefinition = type.GetGenericTypeDefinition();
					if (_exactGenericTypes.TryGetValue(typeDefinition, out value))
						return true;
				}
			}
			
			if (type.IsInterface)
			{
				// In one of the following blocks we will get the interfaces of the actual type.
				// But, if the actual type is an interface also, getting it's interfaces
				// will not get the type itself, so we must check for it.
				if (type.IsGenericTypeDefinition)
				{
					if (_genericInterfaceTypes.TryGetValue(type, out value))
						return true;
				}
				else
				{
					if (_interfaceTypes.TryGetValue(type, out value))
						return true;

					if (type.IsGenericType)
					{
						Type typeDefinition = type.GetGenericTypeDefinition();
						if (_genericInterfaceTypes.TryGetValue(typeDefinition, out value))
							return true;
					}
				}
			}
			else
			{
				Type baseType = type;
				
				if (baseType != typeof(object))
				{
					// we already checked for the first item it the type is a generic one,
					// so we don't do it again.
					if (type.IsGenericType && !type.IsGenericTypeDefinition)
						baseType = type.BaseType;
				
					while(baseType != typeof(object))
					{
						if (baseType.IsGenericTypeDefinition)
						{
							if (_inheritedGenericTypes.TryGetValue(baseType, out value))
								return true;
						}
						else
						{
							if (_inheritedTypes.TryGetValue(baseType, out value))
								return true;

							if (baseType.IsGenericType)
							{
								Type typeDefinition = baseType.GetGenericTypeDefinition();
								if (_inheritedGenericTypes.TryGetValue(typeDefinition, out value))
									return true;
							}
						}
					
						baseType = baseType.BaseType;
					}
				}
			}
			
			var orderedInterfaces = type.GetOrderedInterfaces();
			foreach(Type interfaceType in orderedInterfaces)
			{
				if (_interfaceTypes.TryGetValue(interfaceType, out value))
					return true;

				if (interfaceType.IsGenericType)
				{
					Type genericTypeDefinition = interfaceType.GetGenericTypeDefinition();
					if (_genericInterfaceTypes.TryGetValue(genericTypeDefinition, out value))
						return true;
				}
			}

			if (type.IsInterface)
				return _inheritedTypes.TryGetValue(typeof(object), out value);

			return _inheritedTypes.TryGetValue(typeof(object), out value);
		}
	}
}

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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
Engineer Microsoft Corporation
United States United States
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.
 
Now I just started working as a Senior Software Engineer at Microsoft.
 
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 2013-2014

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