Get method names of un-managed components from Prog Ids using C#

I want to get the method names of un-managed components. I would be doing using the prog-id

System.Type wiType = System.Type.GetTypeFromProgID("Wind开发者_Go百科owsInstaller.Installer");
object objWI = System.Activator.CreateInstance(wiType);

//Type ty = objBLType.GetType();
foreach (MethodInfo mem in wiType.GetMethods())
{
  Console.WriteLine(mem.Name.ToString());
}

Running this doesnt give the method names in WindowsInstaller.Installer.

How can this be achieved. Thanks in advance