C#: How to call a second-level base class method like base.base.GetHashCode()

Question

    class A
    {
        public override int GetHashCode()
        {
            return 1;
        }
    }
    class B : A
    {
        public override int GetHashCode()
        {
            return ((object)this).GetHashCode();
        }
    }

new B().GetHashCode()

this overflows the stack. how can i call Object.GetHashCode from B.GetHashCode()?

edit: B now inherits from A.

Answer 1

(edit - misread question)

If you want to get the original object.GetHashCode() version; you can't - at least, not unless A makes it available via something like:

protected int GetBaseHashCode() { return base.GetHashCode();}

(and have B call GetBaseHashCode()).

The reason it overflows is that GetHashCode is (obviously) virtual - it doesn't matter if you cast it to object; it still starts at the most-derived implementation in the actual object, i.e. B.GetHashCode() (hence the explosion).

Answer 2

At first it looks like you are right: it is impossible. However i have found a way by "cheating":

return (int)typeof(object).GetMethod("GetHashCode").Invoke(this, null);

Answer 3

You can use RuntimeHelpers.GetHashCode(object) to get the original hash code of the object:

  class A
  {
    public override int GetHashCode()
    {
      Console.WriteLine("base hashcode is: " + base.GetHashCode());

      return 1;
    }
  }

  class Program
  {
    public static void Main(string[] args)
    {
      A a = new A();

      Console.WriteLine("A's hashcode: " + a.GetHashCode());

      Console.WriteLine("A's original hashcode: " + RuntimeHelpers.GetHashCode(a));
    }
  }

This produces the following result:

base hashcode is: 54267293
A's hashcode: 1
A's original hashcode: 54267293

If you take a look at RuntimeHelpers.GetHashCode(object) in Reflector, you'll see that it calls the internal static method object.InternalGetHashCode(object). If you'd like to know more, have a look at this question regarding the default implementation of GetHashCode.