using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var cache = new TypeKeyedDictionary<ITom>();

        var tom = new Tom();

        var tomTom = new TomTom();

        cache.Set(tom);

        ITom tomtomtom = cache.Get<Tom>();

        tomtomtom.SayHi();  // prints "I'm Tom"

        try

        {

            cache.Get<TomTom>();

        }

        catch (KeyNotFoundException e)

        {

            Console.WriteLine(e);  // prints "Type TomTom does not exist in dictionary"

        }

        cache.Set(tomTom);

        tomtomtom = cache.Get<TomTom>();

        tomtomtom.SayHi();  // prints "I'm TomTom"

    }

}

​

public interface ITom

{

    void SayHi();

}

​

public class Tom : ITom

{

    public void SayHi()

    {

        Console.WriteLine("I'm Tom");

    }

}

​

public class TomTom : ITom

{

    public void SayHi()

    {

        Console.WriteLine("I'm TomTom");

    }

}

​

public class TypeKeyedDictionary<T> where T : class

{

    private readonly IDictionary<Type, T> _dictionary;

    public TypeKeyedDictionary()

    {

        _dictionary = new Dictionary<Type, T>();

    }

​

    public void Set<TValue>(TValue value) where TValue : T

    {

        Type type = typeof(TValue);

​

        _dictionary[type] = value;

    }

​

    public TValue Get<TValue>() where TValue : T

    {

        Type type = typeof(TValue);

​

        if (Has<TValue>() == false)

        {

            // string interpolation isn't working here? :(

            throw new KeyNotFoundException(string.Format("Type {0} does not exist in dictionary", type));

        }

​

        return (TValue) _dictionary[type];

    }

​

    public void Remove<TValue>() where TValue : T

    {

        Type type = typeof(TValue);

​

        _dictionary.Remove(type);

    }

​

    public bool Has<TValue>() where TValue : T

    {

        Type type = typeof(TValue);

​

        return _dictionary.ContainsKey(type);

    }

}