Calling back to VBScript from C#

Question

Hi,

I'd liked to know whether it is possible to call a function in VBScript from C#. Let me try to clarify. I'm using an application (Quick Test Professional or "QTP") that automates another application, mostly using VBScript. There is the ability, via an add in model, to extend the test functionality by writing add-ins to the testing application (QTP) that are .NET assemblies. The basic workflow is that the VBScript tests automate the test application, and can call methods on a class in the extensibility add in assembly to do more complicated things. This part works fine.

What I'd like to know is whether it is possible for my C# code (in the extensibility add in assembly) to call back to a function in the VBScript. I don't think the test application framework (QTP) explicitly supports this, so I'm wondering if there is any way to do this using standard interop techniques. I was half way thinking of using GetRef() to get a reference to the VBScript function of interest, passing this as a parameter to a method I call in the extensibility addin (I suspect I would run into marshaling issues even at this point?) and then within the C# code of my extensibility add in, somehow call a method on this object; this is where I'm completely lost (since I don't know how to do this without the necessary type information normally used in reflection).

I'm thinking this may not be possible, but would like confirmation if that's the case.

Thank you!

Answer 1

How does the VBScript call the C# code? I suspect that it is really calling on QTP, and QTP is calling the C# code. In that case, only QTP could possibly call the VBScript back.

Under what circumstances would your C# code call back? I doubt that VBScript can be called back asynchronously.

Answer 2

That's a toughie.

You MAY want to try writing an event handler in the VBScript side for the .NET component and raising an event on the .NET side when you want the function to be called.

Just be warned it may not even work, as it really depends on QTP's scripting engine. And even if it should, don't be surprised if it becomes an exercise in frustration.

See examples on WSH and event handling http://msdn.microsoft.com/en-us/library/ms974564.aspx Again, this probably won't apply to QTP, but it's to give you an idea of potential approach to the problem.

Edit: Additional link which may or may not help!

http://www.west-wind.com/presentations/dotnetfromVfp/DotNetFromVfp_EventHandling.asp