I would like to design an app that queries the system for all controls that
implement a particular interface, as well as design some of the controls that
implement these interfaces.  Then in the future, I can just design new controls
with the same interface, without having to change the main app.

I thought I could use the Implements keyword in the control for an interface I
design in a separate class module, but when I try to use such a control, (1) I
can't see or use the interface methods/properties of the control's variable, and
(2) I can't Set another variable (with type equal to the base interface type)
equal to the control variable.

For example,  let's say I have a VB activeX control project.  In that project, I
have a class module (call it ITest), with one method:

Public Sub TestMethod()
End Sub

And also in the project, I have a User Control (call it TestControl).

In the TestControl code, I put:

Implements ITest

Private Sub ITest_TestMethod()
    Beep
End Sub

This control compiles just fine.

Then I create a standard exe, where I put a TestControl (call it TestControl1)
on the main form.

Then if I do:

Private objTest as ITest

and in the form's load function:

Set objTest = TestControl1
(This fails.)

TestControl1.TestMethod
(This also fails -- TestMethod doesn't even show up in the drop-down list of
TestControl1's member functions.)

If anyone could give me some insight as to what I might be doing wrong, I would
greatly appreciate it.  I also would like to hear ideas on how to determine
which controls support a specific interface (if this is even possible -- I would
think it should be).

*************************************************
Patrick Noffke
QTI
Sussex, WI
*************************************************

Thanks!  That solved one problem.

Could you (or someone else) please give a brief description of how to do this in
VB?

If anyone is interested, I found a sample that does this in VC++.  Here is the
link:

http://msdn.microsoft.com/library/periodic/period97/snap797.htm

Pat

There's a sample in my site.

--
Eduardo A. Morcillo
http://www.domaindlx.com/e_morcillo

Thanks for the help thus far.  I've been able to do everything I wanted with
a combination of VB and ATL and the EnumControls example from your site.

I created a component category and modified the ATL code that registers the
control so that it also registers it as belonging to my category.  I did
this using the ICatRegister COM interface.

But it would be nice to be able to do this in VB somehow.  Is there someway
to customize the registration of an ActiveX control so that it registers it
as belonging to a custom Category (i.e. register it as implementing my
CATID)?  I want to be able to do this registration at install time.

Pat