Question

This is a question about design approach. I have limited COM experience and a little WCF experience. My constraints are given by the application environment, but I have some design flexibility.

From within a VB6 dll, I need to start, and communicate with, a WPF application. The WPF application is currently an exe, but I could make it a library if that helped. I would like to provide two way communication between the VB6 dll and the WPF application. I have some flexability to adjust the design of the VB6 dll.

I’m developing C# using in VS2010 and .NET 4.

How many components should I use? Can I start the WPF application In-Proc with the VB6 dll? Should there be a third component between them? Can COM+ play a helpful role? Do I have to make the entire WPF application COM-visible? Is there a down-side to doing this?

I’m looking for a design approach that I can prototype. I’m willing to research the details.

Answer 1

I would

1. Create a Web Service from the WPF application, using WCF. I would abstract out those aspects of the WPF application which should be accessed remotely. This would explicitly not include any of the user interface code.
2. I would create a simple class library project, and use “Add Service Reference” to add a reference to the WCF service.
3. I would make the methods of the class library COM-visible
4. I would call those methods from VB6

This has the benefit of removing any considerations of user interface from the equation.