Question

we have a nasty (or maybe a trivial?) issue.

There is a WPF control. It has 2 interfaces, the main and one for automated testing purpose. Defined this way:

[ComVisible(true)]
[Guid("xxx")]
public interface IXXXXXTest
{
[DispId(1)]
    void Test1(int index);
}

[ComVisible(true)]
public interface IXXXXX
{
    void Main1(index);
}

[ComVisible(true)]
[Guid("xxx")]
ClassInterface(ClassInterfaceType.None)]
public partial class XXXXX_WPF_CONTROL : UserControl,
                         IXXXXX,
                         IXXXXXTest
{
     ...
}

Now we are trying to reach it from VBS.
Try 1)

Set Ctrl = GetControl(...)  <---- this is ok
Ctrl.Test1(0)  <---- Object doesn't support this property or method: 'Ctrl.Test1'

Set Ctrl = GetControl(...)  <---- this is ok
Ctrl.Main1(0)  <---- this is ok

So it works fine for the “main” interface but for the test interface.
This seems ok(?), because as far as I know VBS reaches the “main” interface only via IDispatch if there is no IDispatchEx. So I added a property to the IXXXXX to get the test interface.

[ComVisible(true)]
public interface IXXXXX
{
    void Main1(index);
    IXXXXXTest Test { get;}
}
....
public IXXXXXTest Test
{
    get {   return this as IXXXXXTest;  }
}

Great, so now I can reach this IXXXXTest interface via the “main” interface.
Try 2)

VBS:

Set Ctrl = GetControl(...)  <---- this is ok
Set CtrlTest = Ctrl.Test  <----- this is ok
CtrlTest.Test1(0)    <---- Object doesn't support this property or method: 'CtrlTest.Test1'

🙁

Note that, for an other .NET control of us the “Try1” works, without any trick!

So probably due to the WPF something different?
Also, changing the

ClassInterface(ClassInterfaceType.None)]

into anything else (AutoDispatch / AutoDual), or leaving it makes the WPF control unusable.

Besides that this is also how it should be by this article: Is it possible to package WPF window as COM Object

Do you have any idea what could be the problem?
Thank much in advance!

Answer 1

Scripting languages can only use the default interface on a class. You’ve got more than one so at least one of them will not be usable. And method names may be renamed if they conflict with other declarations. I’d assume you obfuscated the real names in your question so hard to diagnose such a renaming happening from what you posted.

Best thing to do is to temporarily apply the [InterfaceType(ComInterfaceType.InterfaceIsDual)] attribute on your interface types. Which allows you to generate a type library with Tlbexp.exe which you can then view with the OleView.exe utility, File + View Typelib command. You’ll see the exact names of the methods and you’ll see which interface is the [default] one on the coclass. From there you should have little trouble modifying your declarations so they’ll work in a scripting language.