I wrote a VS.NET 2005 class library that I wanted to use from Delphi. Using COM Interop, this should be a breeze. Simply call "regasm MyLibrary.dll /tlb" and I should get a type library that I can import in Delphi. If that's all there was to it, then I wouldn't be blogging.

The first problem I had was that when I ran this command, I got an error stating:
RegAsm error: Failed to load 'C:\MyLibrary.dll' because it is not a valid .NET assembly

This was weird, considering it was a .NET assembly. The problem was that the regasm being used was the one from the .NET 1.1 framework, so it choked on my .NET 2.0 compiled application. Simply running the VS 2005 Command Prompt and re-running regasm got the type library I wanted - or so I thought.

I marked the classes I wanted exported via COM with the [ComVisible(true)] attribute, but the only thing exported to the type library was classes with no members. In order to get the members exported, I ended up putting the [ClassInterface(ClassInterfaceType.AutoDual)] attribute on the class, too. This isn't the optimal approach, according to MSDN, so I'll end up extracting the members to an interface and exposing that instead, but at least I'm up and running for the moment.