wrapping an MFC Gui app into a DLL(or something else) for .NET interop

Question

sound like a terrible idea? Yeah I thought so too. Needless to say im told I have to do it.

Situation: Old MFC-based C++ gui application that reads and processes a whole lot of data sources into an internal datastructure, before displaying it to the user.

Problem: I need that datastructure in .NET, in XML will do.

Solution:

1. Make a function in the MFC app that writes the datastructure to a big XML string(easy).
2. dllexport this function(or COM?)(as a C++ or C funtion or what?)
3. Compile the MFC GUI app into a dll(how?).
4. ???
5. Reference the dll from .NET and P/Invoke method for great profit.

Is this insanity? Is it possible to compile a dll library from a GUI MFC app without changing it? Is it a horrible idea? What are my alternatives? Im pretty lost tbh.

Answer 1

I would be working on extracting the specific business logic code in the MFC app and sticking that stuff in a DLL, rather than trying to wrap up the whole app.

You might be making a false assumption here that it will take you less effort to wrap the MFC app up as a DLL (basically removing all the GUI code, adding a DLL main and modifying the build process to produce a DLL), than the effort to isolate the business logic code and put that in a new DLL project.

To wrap the GUI up as a DLL you will need a pretty good understanding of the dependencies of the business logic code and how it is used by the GUI, so you may as well just cut that stuff out.

Answer 2

Can you change the MFC source just a little? Why not add some command-line parameters to cause the app to spit XML to std output instead of launching GUI?

In CWinApp::InitInstance you have access to command-line paramters by inheriting CCommandLineInfo.

From the .Net client, launch the process and capture the output.