字典中的接口元组键

Question

For all the entities in my project I have a base entity and from that interface another interface and then a class ( this is how it is and I cannot change it ).

Given any 2 objects, I want to call a method. I have created a dictionary with a tuple key to be able to retrieve the right method.

This is the code:

public interface IAnimal
{
    string Name { get; set; }
}

public interface IDog : IAnimal
{

}

public interface ICat : IAnimal
{

}

public interface IMouse : IAnimal
{

}

public class Cat : ICat
{
    public string Name { get; set; }
}

public class Dog : IDog
{
    public string Name { get; set; }
}

public class Mouse : IMouse
{
    public string Name { get; set; }
}

public class Linker
{
    private static Dictionary<Tuple<Type, Type>, object> _linkMethodsDictionary = new Dictionary<Tuple<Type, Type>, object>();

    private static bool _linkDictionaryWasInitialized = false;

    public void InitializeLinkMethods()
    {
        if (_linkDictionaryWasInitialized) return;

        _linkMethodsDictionary.Add(Tuple.Create(typeof(IDog), typeof(ICat)), (Action<IDog, ICat>)LinkDogToCat);
        _linkMethodsDictionary.Add(Tuple.Create(typeof(ICat), typeof(Mouse)), (Action<ICat, IMouse>)LinkCatToMouse);
        _linkDictionaryWasInitialized = true;
    }

    public void Link<T, TU>(T entity1, TU entity2) where T : class, IAnimal
        where TU : class, IAnimal
    {
        Action<T, TU> linkMethod = _linkMethodsDictionary[Tuple.Create(typeof(T), typeof(TU))] as Action<T, TU>;
        if (linkMethod == null)
            throw new NotImplementedException($"Could not find link method for {entity1.Name} and {entity2.Name}");
        linkMethod(entity1, entity2);
    }

    public void LinkDogToCat(IDog dog, ICat cat)
    {
        Console.WriteLine($"Dog: {dog.Name} - Cat:{cat.Name}");
    }

    public void LinkCatToMouse(ICat cat, IMouse mouse)
    {
        Console.WriteLine($"Cat: {cat.Name} - Mouse:{mouse.Name}");
    }

Not sure how to declare the key of the dictionary, because the call fails: "The given key was not present in the dictionary."

        Linker linker = new Linker();
        linker.InitializeLinkMethods();

        ICat cat = new Cat() {Name = "The CAT"};
        IDog dog = new Dog() {Name = "the DOG"};
        IMouse mouse = new Mouse() {Name = "The MOUSE"};


        linker.Link<ICat, IMouse>(cat, mouse);
        linker.Link(dog, cat);

Answer 1

I have used a struct as a key for the Dictionary

 internal struct EntityLinkKey
 {
    private readonly Type _first;

    private readonly Type _second;

    public EntityLinkKey(Type first, Type second)
    {
        this._first = first;
        this._second = second;
    }

    public override int GetHashCode()
    {
        return this._first.GetHashCode() * 17 + this._second.GetHashCode();
    }

    public override bool Equals(object obj)
    {
        if (ReferenceEquals(null, obj)) return false;
        if (GetType() != obj.GetType()) return false;

        EntityLinkKey p = (EntityLinkKey)obj;
        return p._first == this._first && p._second == this._second;
    }
}