Re: How to expose IDispatch on an internal class

Marvin Landman <marvin@newsgroup.nospam>
Wed, 02 Sep 2009 18:56:19 +0200

The client component is Windows Script Host, but I was able to reproduce
the same problem by using GetIDispatchForObject that I believe is
calling the same internal marshaling function as the automatic marshaler.

My problem is that I get InvalidCastException for
"Marshal.GetIDispatchForObject (mc)"

When I change "internal class MyClass : IMyInterface" to "public class
MyClass : IMyInterface" the exception is gone and everything works as

My problem is that I would like to expose the IDispatch object to COM
componenets (Windows Script Host) but I don't want to expose those
objects to managed applications.

using System;
using System.Runtime.InteropServices;

namespace InternalIDispatch
    [ClassInterface (ClassInterfaceType.None)]
    [ComVisible (true)]
    internal class MyClass : IMyInterface
        public void MyMethod ()
            Console.WriteLine ("MyMethod");

    [InterfaceType (ComInterfaceType.InterfaceIsDual)]
    internal interface IMyInterface
        void MyMethod ();

    internal class Program
        private static void Main (string [] args)
            MyClass mc = new MyClass ();

            Console.WriteLine (Marshal.GetIDispatchForObject (mc));
            Console.ReadLine ();



Jie Wang [MSFT] wrote:

Hi Marvin,

What is the client of the component? VB6? Native VC++? Or something else?

Please let me know more about the detailed configuration so I can try repro
the scenario and find out more.

Jie Wang

Microsoft Online Community Support

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