如何确定类型是否实现接口并使用该接口的成员

Question

I am building a Vector<T> class and I am having differculties with an Add method. What I already have is the interface that makes adding possible, but only if I know that T implements IAddable<TIn, TOut> .

interface IAddable<TIn, TOut>
{
    Vector<TOut> Add(Vector<TIn>)
}

partial Vector<T> where T : IAddable<T, T>
{
    public Vector<T> Add(Vector<T> v)
    {
        return mapIndexed((index, x) => this[index].Add(v[index]));
    }
}

The point is, I want to be able to add Vector<T> and Vector<TIn> to a Vector<TOut> for every T that implements IAddable<TIn, TOut> . My solution below obviously doesn't work because you can't just call this[index].Add(v[index]) . Is there a way to call it without running into this kind of problems?

partial Vector<T>
{
    public Vector<TOut> Add<TIn, TOut>(Vector<TIn> v)
    {
        if (typeof(T).IsAssignableFrom(typeof(IAddable<TIn, TOut>)))
            return mapIndexed((index, x) => this[index].Add(v[index]));
        return null;
    }
}

Answer 1

If T.GetInterface("IAddable<TIn, TOut>") != null { /* Use in vector... */ }

Answer 2

Actually, no need for contrvariance here. The following will allow to add a Vector<T> into Vector<T2> only if T2 is derives from T

public interface IMyVector<T>
{
    void AddVector<TIn>(IMyVector<TIn> vector) where TIn : T;
}

public class Vector<T> : IMyVector<T>
{
    public void AddVector<TIn>(IMyVector<TIn> vector) where TIn : T
    {
        // Your logic here
    }
}

public class Base {}

public class Derived : Base {}

And the test class:

public class Tests
{
    public void Test()
    {
        IMyVector<Base> baseVector= null;
        IMyVector<Derived> derivedVector= null;

        baseVector.AddVector(derivedVector);
    }
}