Question

why invoking a method by reflection is much slower than making a interface then recall it by reflection. the first version shows the tedious way the other version shows the enhanced way??

 // first version
  class A
    {
        public void fn()
        { 
        }
    }
  void Main(String[]x)
  {
        Type type = typeof(A);
        object obj = Activator.CreateInstance(type);
        type.InvokeMember("fn", BindingFlags.Public, null, obj, null);
  }

  //second verison
   interface IA
    {
        void fn();
    }

    class A :IA
    {
        public void fn()
        {
        }
    }

 void Main(String []x)
 {
        Type type = typeof(A);
        IA obj =(IA) Activator.CreateInstance(type);
        obj.fn();
 }

Answer 1

Reflection-based method calls are extremely slow, since you need to do member lookup and parameter binding and other things at runtime.

Interface methods, by contrast, are called with a regular callvirt instruction using the vtable.