Why does dynamic binding fail when using interface inheritance?

Question

In C#, please does anyone know why I can't do the following? (specifically the line marked 'NOT fine!' below)

interface A {     void Add(dynamic entity); }  interface B : A {}  class C : B {     public void Add(dynamic entity)     {         System.Console.WriteLine(entity);     } }  class Program {     static void Main(string[] args)     {         B b = new C();         dynamic x = 23;         b.Add(23);        // fine         b.Add((int)x);    // fine         (b as A).Add(x);  // fine         //b.Add(x);       // NOT fine!     } } 

I have absolutely no problems if the call isn't dynamically-bound, or if I explicitly cast to the interface at the root of the hierarchy, but the dynamically-bound call gives me:

Unhandled Exception: Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: No overload for method 'Add' takes '1' arguments    at CallSite.Target(Closure , CallSite , B , Object )    at System.Dynamic.UpdateDelegates.UpdateAndExecuteVoid2[T0,T1](CallSite site, T0 arg0, T1 arg1)    at Program.Main(String[] args) in C:\Users\Stuart\Documents\Visual Studio 2010\Projects\CSharp Testbed\Program.cs:line 218 

Answer 1

Looking on Microsoft Connect it's filed as a bug - Dynamic runtime fails to find method from a base interface during runtime