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Lazy Alternatives - LazyAndWeak and BackgroundLoader

, 1 Dec 2011 CPOL
This article will present two alternatives to Lazy.
LazyAlternatives
LazyAlternatives.suo
LazyAlternativesSample
Properties
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.Reflection;
using System.Runtime.Serialization;
using Pfz.Serialization;

namespace Pfz.Extensions
{
	/// <summary>
	/// Adds some methods for clonning objects.
	/// </summary>
	public static class PfzClonningExtensions
	{
		/// <summary>
		/// Clones the source object returning the new one as the same type
		/// (cast) of the original.
		/// </summary>
		public static T TypedClone<T>(this T source)
		where
			T: ICloneable
		{
			if (source == null)
				throw new ArgumentNullException("source");
				
			return (T)source.Clone();
		}

		/// <summary>
		/// Does a clone of an ICloneable&lt;T&gt;, checking if the source is null.
		/// If it is, returns null, instead of throwing an exception.
		/// </summary>
		public static T CheckedClone<T>(this T source)
		where
			T: ICloneable<T>
		{
			if (source == null)
				return source;

			return source.Clone();
		}
	}

	#if WINDOWS_PHONE
	#else
	namespace ClonningExtensions
	{
		/// <summary>
		/// Class that contains CloneBySerialization method.
		/// As the name says, it adds a method that allows to deep-clone objects, using a process similar
		/// to serialization/deserialization.
		/// </summary>
		public static class PfzCloneBySerializationExtension
		{
			/// <summary>
			/// Clones an object by using a process similar to serialization/deserialization.
			/// </summary>
			public static T CloneBySerialization<T>(this T source)
			{
				if (source == null)
					throw new ArgumentNullException("source");
			
				List<IDeserializationCallback> callbacks = new List<IDeserializationCallback>();
				Dictionary<object, object> clonnedObjects = new Dictionary<object, object>(ReferenceComparer.Instance);
				object result = _Clone(callbacks, clonnedObjects, source);
			
				StreamingContext context = new StreamingContext(StreamingContextStates.Clone);
			
				foreach(var callback in callbacks)
					callback.OnDeserialization(context);
			
				return (T)result;
			}
			private static object _Clone(List<IDeserializationCallback> callbacks, Dictionary<object, object> clonnedObjects, object graph)
			{
				if (graph == null)
					return null;
			
				// strings are read-only, so no clonning is needed.
				if (graph is string)
					return graph;
				
				// optimization for DBNull
				if (graph == DBNull.Value)
					return DBNull.Value;
			
				// optimization for MemberInfos in general.
				if (graph is MemberInfo)
					return graph;
			
				StreamingContext context = new StreamingContext(StreamingContextStates.Clone);
				OldBinarySerializerBase._InvokeOnSerializing(graph, context);
				object result = _Clone2(callbacks, clonnedObjects, graph);
				OldBinarySerializerBase._InvokeOnSerialized(graph, context);
				OldBinarySerializerBase._InvokeOnDeserialized(result, context);
				return result;
			}
			private static object _Clone2(List<IDeserializationCallback> callbacks, Dictionary<object, object> clonnedObjects, object graph)
			{
				Type type = graph.GetType();
			
				if (!type.IsSerializable)
					throw new ArgumentException("graph of type " + type.FullName + " is not serializable.");
			
				object result = null;
				if (!type.IsValueType)
					if (clonnedObjects.TryGetValue(graph, out result))
						return result;
			
			
				if (type.IsArray)
				{
					Array sourceArray = (Array)graph;
					Array resultArray = (Array)sourceArray.Clone();
				
					_AddClonnedObject(graph, resultArray, callbacks, clonnedObjects);
				
					Type elementType = type.GetElementType();
					if (!_HasAnyReference(elementType))
						return resultArray;
					
					int dimensions = resultArray.Rank;
					int[] indices = new int[dimensions];
					for (int i=0; i<dimensions; i++)
						indices[i] = resultArray.GetLowerBound(i);
				
					int lastDimension = dimensions-1;
					indices[lastDimension]--;

					while(true)
					{
						int actualDimension = lastDimension;
						while(true)
						{
							int index = indices[actualDimension] + 1;
							if (index <= resultArray.GetUpperBound(actualDimension))
							{
								indices[actualDimension] = index;
								object item = _Clone(callbacks, clonnedObjects, resultArray.GetValue(indices));
								resultArray.SetValue(item, indices);
								break;
							}

							if (actualDimension == 0)
								return resultArray;
							
							indices[actualDimension] = resultArray.GetLowerBound(actualDimension);
							actualDimension--;
						}
					}
				}

				ISerializable serializable = graph as ISerializable;
				if (serializable != null)
				{
					SerializationInfo info = new SerializationInfo(type, new FormatterConverter());
					StreamingContext context = new StreamingContext(StreamingContextStates.Clone);
					serializable.GetObjectData(info, context);
				
					ConstructorInfo constructorInfo = null;
				
					if (info.AssemblyName == type.Assembly.FullName && info.FullTypeName == type.FullName)
					{
						result = OldBinarySerializerBase._FormatterServicesGetSafeUninitializedObject(type, new StreamingContext(StreamingContextStates.Clone));
					
						_AddClonnedObject(graph, result, callbacks, clonnedObjects);

						constructorInfo = type.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, OldBinarySerializerBase._deserializationConstructorTypes, null);
					}
					else
					{
						Type realType = Assembly.Load(info.AssemblyName).GetType(info.FullTypeName, true);
						constructorInfo = realType.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, OldBinarySerializerBase._deserializationConstructorTypes, null);
					}

					if (constructorInfo == null)
						throw new SerializationException("Couldn't find Deserialization constructor for type " + type.FullName + ".");
					
					var parameters = new object[]{info, context};
				
					if (result != null)
						constructorInfo.Invoke(result, parameters);
					else
					{
						result = constructorInfo.Invoke(parameters);

						IObjectReference objectReference = result as IObjectReference;
						if (objectReference != null)
						{
							result = objectReference.GetRealObject(context);
						
							IDeserializationCallback callback = objectReference as IDeserializationCallback;
							if (callback != null)
								callbacks.Add(callback);
						}

						_AddClonnedObject(graph, result, callbacks, clonnedObjects);
					}

					return result;
				}
			
				result = OldBinarySerializerBase._FormatterServicesGetSafeUninitializedObject(type, new StreamingContext(StreamingContextStates.Clone));
			
				_AddClonnedObject(graph, result, callbacks, clonnedObjects);

				var fields = OldBinarySerializerBase._GetFields(type);
				object[] values = FormatterServices.GetObjectData(graph, fields);
				int length = values.Length;
				for (int i=0; i<length; i++)
				{
					object value = values[i];
					if (value != null && _HasAnyReference(value.GetType()))
					{
						value = _Clone(callbacks, clonnedObjects, value);
						values[i] = value;
					}
				}
				FormatterServices.PopulateObjectMembers(result, fields, values);
				return result;
			}

			private static void _AddClonnedObject(object graph, object result, List<IDeserializationCallback> callbacks, Dictionary<object, object> clonnedObjects)
			{
				if (!graph.GetType().IsValueType)
					clonnedObjects.Add(graph, result);
			
				IDeserializationCallback callback = result as IDeserializationCallback;
				if (callback != null)
					callbacks.Add(callback);
			}

			private static Dictionary<Type, bool> _hasAnyReferenceDictionary = new Dictionary<Type, bool>();
			private static bool _HasAnyReference(Type type)
			{
				if (type.IsPrimitive)
					return false;
			
				if (!type.IsValueType)
					return true;
				
				if (type == typeof(string))
					return false;
			
				if (typeof(ISerializable).IsAssignableFrom(type))
					return true;
			
				lock(_hasAnyReferenceDictionary)
				{
					bool result;
				
					if (!_hasAnyReferenceDictionary.TryGetValue(type, out result))
					{
						FieldInfo[] fields = OldBinarySerializerBase._GetFields(type);
						foreach(var field in fields)
						{
							if (_HasAnyReference(field.FieldType))
							{
								result = true;
								break;
							}
						}
					
						_hasAnyReferenceDictionary.Add(type, result);
					}
				
					return result;
				}
			}
		}
	}
	#endif
}

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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 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.

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, 2015 & 2016
Microsoft MVP 2013-2014 (now I work at Microsoft so I can't be a Microsoft MVP anymore)

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