How can I debug a C# COM assembly when it's being called from a native win32 application?

Question

I'm developing a C# assembly which is to be called via COM from a Delphi 7 (iow, native win32, not .net) application.

So far, it seems to work. I've exported a TLB file, imported that into my Delphi project, and I can create my C# object and call its functions.

So that's great, but soon I'm going to really want to use Visual Studio to debug the C# code while it's running. Set breakpoints, step through code, all that stuff.

I've tried breaking in the Delphi code after the COM object is created, then looking for a process for VS to attach to, but I can't find one.

Is there a way to set VS2008 up to do this? I'd prefer to just be able to hit f5 and have VS start the Delphi executable, wait for the C# code to be called, and then attach itself to it.. But I could live with manually attaching to a process, I suppose.

Just please don't tell me I have to make do with MessageBox.Show etc.

Answer 1

Place the following in the method you wish to debug:

#if DEBUG
    if (!System.Diagnostics.Debugger.IsAttached)
     Debugger.Launch();
#endif

When you want to debug, build a debug version and use that in your application. When this code runs, a dialog pops up asking if you want to attach a debugger.

Answer 2

You can just attach to the native application and see breakpoint, view stacks, watches etc. normally. You'll need to attach after the COM object is created.

I put a Afx MsgBox when the object is created to stop the application's flow and then attach the debugger.

Answer 3

In the VS2008 project properties page, on the Debug tab, there's an option to set a different Start Action.

This can be used to run an external program (e.g. your Delphi app) when you press F5.