C# Auto-Casting Interface Methods

Question

I have an an interface which uses an abstract class in its signature. My implementations then use the a subclass of the abstract class in their signature but this is not allowed. Can someone help me out? All I can find on the googles is generic interface and abstract class implementations...

public MyAbstractClass {
    abstract public void myMethod();
}

public MySubClass : MyAbstractClass {
    override public void myMethod(){
        ...
    }
}

And then I have my interface/implementation..

public interface MyInterface {
    MyAbstractClass myInterfaceMethod(MyAbstractClass blah);
}

public MyImplementation : MyInterface {
    MySubClass myInterfaeMethod(MySubClass blah){
        ...
    }
}

But I get an error building saying myInterfaceMethod doesn't implement the interfaces method...

Help?

score 6 · Accepted Answer · answered Nov 11 '15 at 17:31

You can't do that because it violates the interface. You can however make MyInterface generic.

public interface MyInterface<T> where T: MyAbstractClass {
    T myInterfaceMethod(T blah);
}

public MyImplementation : MyInterface<MySubClass> {
    MySubClass myInterfaeMethod(MySubClass blah){
        ...
    }
}

C# Auto-Casting Interface Methods

1 Answers1