Making a DLL COM accessible

Question

I have a class library written in .Net that I would like to make available to VB6/VBA. What I tried did not work (obviously as I am asking this question). Here is what I did:

1. I Created a Class Library Project in Visual Studio 2010 Express and put the code in a Class Module.
2. I opened the project properties and went to "Assembly Information" and checked "Make COM Visible".
3. I went to "Advanced Compile" options and targeted .Net 2.0 (it's very simple code).
4. I then removed all references expect for "System".
5. I built the project (no warnings or errors) and copied the DLL out of the Bin folder into C:\Windows\System32\
6. I ran RegSvr32 to register the DLL and got the error:

The module "MyDll.dll" was loaded but the entry-point DLLRegisterServer was not found.

Make sure that "MyDll.dll is a valid DLL or OCX file and then try again.

Clearly my first attempt was a bit naive. Could someone offer guidance?

Answer 1

I am fairly certain RegSvr32 only works on non.NET DLL. .NET assemblies are stored in the Global Assembly Cache (GAC). You have to run the gacutil.exe.

Answer 2

Step #6 is wrong. .NET assemblies with [ComVisible] types are registered with Regasm.exe. Use the /codebase command line option if you don't want to install the DLL into the GAC. The /tlb command line option creates the type library, you can use that in your VB6 project.

Answer 3

You'll need to define GUIDs for your interfaces and mark which classes implement which interfaces, to start. MSDN has a getting started guide. You don't need to run RegSvr32, but you do need to put the DLL somewhere where the app can find it:

After registering an assembly using Regasm.exe, you can install it in the global assembly cache so that it can be activated from any COM client. If the assembly is only going to be activated by a single application, you can place it in that application's directory.

There is also a good overview of the whole process here.