KeyedByTypeCollection<TItem> Class

You construct a copy of this class using a class or interface common to all the type you will store. That is just a sanity check, and you can use System.Object if you don't want that. You use the Add method to add values just like any other collection. To look-up a value by type you have two options. You can use a System.Type object as an indexer, and you will receive a reference of the common ancestor type. In the alternative, use the Find method constructed with the type you want to look up, and you get back a reference of exactly that type.

An example utilizing Find: (thanks to Pavel Minae)

using System;
using System.Collections.Generic;
static class Program
{
    static void Main()
    {
        var d = new KeyedByTypeCollection<object>();
        d.Add(123);
        d.Add(123.456);
        d.Add('x');
        d.Add("foo");
        Console.WriteLine(d.Find<int>());
        Console.WriteLine(d.Find<double>());
        Console.WriteLine(d.Find<char>());
        Console.WriteLine(d.Find<string>());
        d.Remove<int>();
        d.Remove<double>();
        d.Remove<string>();
        d.Add('y'); // throws
    }
}