CodeGenerator to generate async interface from sync?

[C# Programming]

If anyone knows or has codegenerator that will create:

public interface IMyInterface
{
IAsyncResult BeginMyMethod(int param,AsyncCallback callback,object state);

int EndMyMethod(IAsyncResult result);
}

from
public interface IMyInterface
{
int MyMethod(int param);
}

I`ve found only java version of it.