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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.Linq;
using System.Reflection;
using System.Runtime.Serialization;
using Pfz.DataTypes;
using Pfz.Extensions;

namespace Pfz.Serialization
{
	/// <summary>
	/// Base class for BinarySerializer and RemotingSerializer.
	/// </summary>
	public abstract class OldBinarySerializerBase
	{
		#region DefaultTypes - Methods
			internal readonly HashSet<Assembly> _defaultAssemblies = new HashSet<Assembly>();
			internal readonly HashSet<Type> _defaultTypes = new HashSet<Type>();
			
			/// <summary>
			/// This method adds a type to the "automatic type list".
			/// This avoids such type to be saved in serialized streams, but the
			/// deserializer must add the exactly same types, in the exactly same
			/// order.
			/// Returns a boolean value indicating if such type was added (true),
			/// or if was already added before (false).
			/// </summary>
			public bool AddDefaultType(Type type)
			{
				if (type == null)
					throw new ArgumentNullException("type");
					
				// unnecessary checks, as the Type can be passed as Content.
				/*if (!type.IsSerializable)
					throw new ArgumentException("type must be serializable.\r\nType: " + type.FullName, "type");
					
				if (type.IsAbstract && type != typeof(Type))
					throw new ArgumentException("type must not be abstract.\r\nType: " + type.FullName, "type");*/
					
				_defaultAssemblies.Add(type.Assembly);
				bool result = _defaultTypes.Add(type);
				return result;
			}
			
			/// <summary>
			/// Adds primitive types as Default-Types.
			/// </summary>
			public void AddPrimitivesAsDefault()
			{
				_defaultAssemblies.Add(typeof(int).Assembly);
				_defaultTypes.Add(typeof(int));
				_defaultTypes.Add(typeof(long));
				_defaultTypes.Add(typeof(byte));
				_defaultTypes.Add(typeof(short));
				_defaultTypes.Add(typeof(uint));
				_defaultTypes.Add(typeof(ulong));
				_defaultTypes.Add(typeof(sbyte));
				_defaultTypes.Add(typeof(ushort));
				_defaultTypes.Add(typeof(bool));
				_defaultTypes.Add(typeof(char));
				_defaultTypes.Add(typeof(float));
				_defaultTypes.Add(typeof(double));
			}
			
			/// <summary>
			/// Adds primitives, string, DateTime, decimal and some other common
			/// types as default types.
			/// </summary>
			public void AddRecommendedDefaults()
			{
				AddPrimitivesAsDefault();
				_defaultAssemblies.Add(typeof(Date).Assembly);
				_defaultTypes.Add(typeof(string));
				_defaultTypes.Add(typeof(decimal));
				_defaultTypes.Add(typeof(Date));
				_defaultTypes.Add(typeof(DateTime));
				_defaultTypes.Add(typeof(Time));
				_defaultTypes.Add(typeof(Type));
				_defaultTypes.Add(typeof(byte[]));
				_defaultTypes.Add(typeof(int[]));
			}
			
			/// <summary>
			/// Adds the given type to the list of default types, and every
			/// type referenced by this type, directly or indirectly, that is
			/// not a value type (as the Type for value type references are 
			/// never serialized).
			/// </summary>
			public void AddDefaultTypeRecursive(Type type)
			{
				if (type == null)
					throw new ArgumentNullException("type");

				if (type.IsArray)
				{
					AddDefaultType(type);
					type = type.GetElementType();
				}

				if (!type.IsAbstract || type == typeof(Type))
					AddDefaultType(type);

				HashSet<Type> abstractTypes = new HashSet<Type>();
				_AddDefaultTypeRecursive(type, abstractTypes);
			}
			private void _AddDefaultTypeRecursive(Type type, HashSet<Type> abstractTypes)
			{
				if (type == typeof(Type))
					return;

				if (typeof(ISerializable).IsAssignableFrom(type))
					return;
					
				var fields = _GetFields(type);
				foreach(var field in fields)
				{
					Type fieldType = field.FieldType;

					if (fieldType.IsArray)
					{
						AddDefaultType(fieldType);
						fieldType = fieldType.GetElementType();
					}
					
					if ((fieldType.IsAbstract && fieldType != typeof(Type)) || (fieldType.IsValueType && (!fieldType.IsGenericType || fieldType.GetGenericTypeDefinition() != typeof(Nullable<>))))
					{
						if (!abstractTypes.Add(fieldType))
							continue;
					}
					else
					{
						if (!AddDefaultType(fieldType))
							continue;
					}
						
					_AddDefaultTypeRecursive(fieldType, abstractTypes);
				}
			}
			
			/// <summary>
			/// Add the nullable version of already added value-type defaults
			/// as default values.
			/// </summary>
			public void AddNullableOfDefaultsAsDefaults()
			{
				bool wasAdded = false;
				var array = _defaultTypes.ToArray();
				foreach(var item in array)
				{
					if (!item.IsValueType)
						continue;
					
					if (item.IsGenericType && item.GetGenericTypeDefinition() == typeof(Nullable<>))
						continue;
					
					var nullableType = typeof(Nullable<>).MakeGenericType(item);
					_defaultTypes.Add(nullableType);
					wasAdded = true;
				}
				
				if (wasAdded)
					_defaultAssemblies.Add(typeof(Nullable<>).Assembly);
			}
		#endregion

		#region _GetFields
			private static Dictionary<Type, FieldInfo[]> _fieldInfos = new Dictionary<Type, FieldInfo[]>();
			internal static FieldInfo[] _GetFields(Type type)
			{
				FieldInfo[] result;
				
				if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>))
					type = type.GetGenericArguments()[0];
				
				lock(_fieldInfos)
				{
					if (_fieldInfos.TryGetValue(type, out result))
						return result;
					
					List<FieldInfo> list = new List<FieldInfo>();
					Type actualType = type;
					while(actualType != null)
					{
						result = actualType.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
						
						foreach(var field in result)
							if (!field.ContainsCustomAttribute<NonSerializedAttribute>() && !field.ContainsCustomAttribute<OptionalFieldAttribute>())
								list.Add(field);
						
						actualType = actualType.BaseType;
					}
					
					result = list.ToArray();
					_fieldInfos.Add(type, result);
				}

				return result;
			}
		#endregion

		#region InvokeAll - Private Methods
			internal static readonly Type[] _deserializationConstructorTypes = new Type[]{typeof(SerializationInfo), typeof(StreamingContext)};
			private static readonly Dictionary<Type, MethodInfo[]> _onSerializings = new Dictionary<Type, MethodInfo[]>();
			internal static void _InvokeOnSerializing(object graph, StreamingContext context)
			{
				_InvokeAllMethodsWith(_onSerializings, graph, typeof(OnSerializingAttribute), context);
			}

			private static readonly Dictionary<Type, MethodInfo[]> _onSerializeds = new Dictionary<Type, MethodInfo[]>();
			internal static void _InvokeOnSerialized(object graph, StreamingContext context)
			{
				_InvokeAllMethodsWith(_onSerializeds, graph, typeof(OnSerializedAttribute), context);
			}
			
			private static readonly Dictionary<Type, MethodInfo[]> _onDeserializings = new Dictionary<Type, MethodInfo[]>();
			internal static void _InvokeOnDeserializing(object graph, StreamingContext context)
			{
				_InvokeAllMethodsWith(_onDeserializings, graph, typeof(OnDeserializingAttribute), context);
			}

			private static readonly Dictionary<Type, MethodInfo[]> _onDeserializeds = new Dictionary<Type, MethodInfo[]>();
			internal static void _InvokeOnDeserialized(object graph, StreamingContext context)
			{
				_InvokeAllMethodsWith(_onDeserializeds, graph, typeof(OnDeserializedAttribute), context);
			}

			private static void _InvokeAllMethodsWith(Dictionary<Type, MethodInfo[]> dictionary, object graph, Type attributeType, StreamingContext context)
			{
				MethodInfo[] result;
				
				Type type = graph.GetType();
				lock(dictionary)
				{
					if (!dictionary.TryGetValue(type, out result))
					{
						List<MethodInfo> list = new List<MethodInfo>();
						Type actualType = type;
						while(actualType != null)
						{
							MethodInfo[] methods = actualType.GetMethods(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
							foreach(var method in methods)
								if (method.GetCustomAttributes(attributeType, false).Length > 0)
									list.Add(method);
						
							actualType = actualType.BaseType;
						}
						
						if (list.Count > 0)
							result = list.ToArray();
							
						dictionary.Add(type, result);
					}
				}
				
				if (result != null)
				{
					var parameters = new object[]{context};
					foreach(var method in result)
						method.Invoke(graph, parameters);
				}
			}
		#endregion

		#region Unclassified
			internal static object _FormatterServicesGetSafeUninitializedObject(Type type, StreamingContext context)
			{
				object result = FormatterServices.GetSafeUninitializedObject(type);
				_InvokeOnDeserializing(result, context);
				return result;
			}
			internal static Assembly _AssemblyLoad(string assemblyName)
			{
				foreach(var assembly in AppDomain.CurrentDomain.GetAssemblies())
					if (assembly.FullName == assemblyName)
						return assembly;

				return Assembly.Load(assemblyName);
			}
		#endregion
	}
}

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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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