Question

I have 2 interfaces and 2 classes that I investigate via Reflection:

• IParent
• IChild – derives from IParent
• Parent
• Child – derives from Parent

Strange thing for me is the fact that when I look through reflection on IChild type I don’t find IParent method.

Same code applied to Child type works as expected – reflection shows Parent method.

interface IParent
{
     void ParentMethod();
}

interface IChild : IParent
{
     void ChildMethod();
}

class Parent 
{
     public void ParentMethod(){}
}

class Child : Parent
{
     public void ChildMethod(){}
}

void Main()
{
    //investigate derived interface
     Type t = typeof(IChild);
     var info = t.GetMethod("ChildMethod");//ok
     Console.WriteLine(info); 
     info = t.GetMethod("ParentMethod");//returns null!
     Console.WriteLine(info); 
     //investigate derived class
     t = typeof(Child);
     info = t.GetMethod("ChildMethod");//ok
     Console.WriteLine(info);
     info = t.GetMethod("ParentMethod");//ok
     Console.WriteLine(info);
}

Please explain such behaviour?

Is there any workaround to reflect base interface’s methods from the derived interface’s type?

Answer 1

Although, we use the interfaces as the same way we use inheritance (“:”); interfaces are not inherited; they are to be implemented. In such a case; inheritance is confused with implementation since they are defined using the same operator (“:”).

As a summary;
IA : IB and A:IA means; any class implementing IA, shall implement IB. In this case; A shall implement IA and IB.

A:B means A class inherits B class; it does not implement.

The confusion here derives from using the same operator (“:”).

Check this page interface inheritance