HashableWeakRef<T> examle

Program.cs

using System;
using System.Collections.Generic;


namespace TestHashableWeakRef
{
	class MainClass
	{
		public static void Main (string[] args)
		{
			object keyObj = new object();

			var dict = new Dictionary<HashableWeakRef<object>, string>();
			var weakKey = new HashableWeakRef<object>(keyObj);

			Console.WriteLine("Setting dict[weakKey]...");
			dict[weakKey] = "value in the dict";
			PrintDict(dict);

			var anotherWeakKey = new HashableWeakRef<object>(keyObj);
			Console.WriteLine("Setting dict[anotherWeakKey]...");
			dict[anotherWeakKey] = "a different value in the dict";
			PrintDict(dict);

			Console.WriteLine("Unsetting dict[weakKey]...");
			dict.Remove(weakKey);
			PrintDict(dict);

			Console.WriteLine("Setting dict[anotherWeakKey]...");
			dict[anotherWeakKey] = "third value";
			PrintDict(dict);

			Console.WriteLine("Setting dict[weakKey]...");
			dict[weakKey] = "final value";
			PrintDict(dict);
		}

		public static void PrintDict(Dictionary<HashableWeakRef<object>, string> dict)
		{
			Console.WriteLine("Printing dictionary:\n{");
			foreach (var key in dict.Keys) {
				Console.WriteLine(string.Format("\tKEY: {0}   VALUE: {1}   WEAKREFHASH: {2}", key, dict[key], key.GetWeakReferenceHashCode()));
			}
			Console.WriteLine("}\n");
		}
	}
}


class HashableWeakRef<T> : IEquatable<HashableWeakRef<T>> where T : class
{
	private WeakReference weakRef;

	public T Target { get { return (T) weakRef.Target; } }

	public HashableWeakRef(T target)
	{
		weakRef = new WeakReference(target);
	}

	public int GetWeakReferenceHashCode()
	{
		return this.weakRef.GetHashCode();
	}

	public override int GetHashCode()
	{
		var tmpTarget = weakRef.Target;
		if (tmpTarget == null) {
			throw new InvalidOperationException("Can't hash a null weak ref");
		}
		return tmpTarget.GetHashCode();
	}

	public override bool Equals(object other)
	{
		if (other is HashableWeakRef<T>) {
			return this.Equals((HashableWeakRef<T>) other);
		}
		return false;
	}

	public bool Equals(HashableWeakRef<T> other)
	{
		var tmpOtherTarget = other.weakRef.Target;
		var tmpThisTarget = this.weakRef.Target;
		if (tmpOtherTarget == null || tmpThisTarget == null) {
			throw new ArgumentNullException("Can't compare null weakrefs");
		}
		return tmpThisTarget.Equals(tmpOtherTarget);
	}

	public static bool operator ==(HashableWeakRef<T> a, HashableWeakRef<T> b)
	{
		var tmpTargetA = (T) a.weakRef.Target;
		var tmpTargetB = (T) b.weakRef.Target;
		if (tmpTargetA == null || tmpTargetB == null) {
			throw new ArgumentNullException("Can't test equality for null weakrefs");
		}
		return tmpTargetA == tmpTargetB;
	}

	public static bool operator !=(HashableWeakRef<T> a, HashableWeakRef<T> b)
	{
		return !(a == b);
	}
}