How to access Interface method implemented in the derived class from child class?

Question

I have two interfaces A,B both has same method declarations. I have a class C inheriting from interfaces A,B. I have another class D inheriting from C. Now i want to access the implemented methods in C from D

interface A
{
    int add(int x, int y);
    int mul(int x, int y);
}

interface B
{
    int add(int x, int y);
    int mul(int x, int y);
}

public class C : A,B
{
    int A.add(int x,int y)
    {
        return x + y;
    }

    int A.mul(int x,int y)
    {
        return 0;
    }

    int B.add(int x, int y)
    {
        return x;
    }

    int B.mul(int x, int y)
    {
        return y;
    }  
}


class D : C
{
}

How to access the methods in C from D?

Answer 1

How to access the methods in C from D?

You have to use a reference with a compile-time of the relevant interface. For example:

class D
{
    public void FooA()
    {
        A a = this;
        Console.WriteLine(a.mul(...));
    }

    public void FooB()
    {
        B b = this;
        Console.WriteLine(b.mul(...));
    }
}

Of course you don't need the local variable - you can cast:

Console.WriteLine(((A) this).mul(...));

... but it gets a bit ugly.

This is just because you're using explicit interface implementation. If you implemented one of the interfaces implicitly, you could just call the methods directly as normal... but explicit interface implementation only allows a member to be called via that interface.

Answer 2

An explicit interface method invocation should always work

((A)this).mul(1,1);