Most of the time when I’m developing and I have to learn something new – a new API, a new event model, etc. – or I just need to try something that I don’t know whether it will work or not I create a new project (often with a name that begins with the prefix of TEST).  These projects are where I prove out the technology before integrating it with the core code of the project.  The test project always gets cataloged into a special place in the source control system, and rarely gets directly moved into the main project.

However, every once in a while I guess right and I put together a technology proof (test if you prefer) that works like I want the production to work like.  Today was one of those rare days when I created a new Workflow Activity the way I wanted it.

After I got it checked in I did a bit of source control work to share the test code over to the core project so I could include the files.  (I branched after the share so the files are now on their own unique paths.)  I added the working activity to my core project and… it didn’t work.  I got this really ugly error when I tried to open the design surface for the activity.  It said in part:

The service 'System.Workflow.ComponentModel.Design.IIdentifierCreationService' must be installed for this operation to succeed. Ensure that this service is available.

After I stared at the screen wondering how to figure this out, searched for answers (and came up with nothing), I started looking into the project file and found that there are two necessary pieces to make the workflow designer surface to work.  The first entry that’s necessary belongs in the <PropertyGroup> and is:

 <ProjectTypeGuids>{14822709-B5A1-4724-98CA-57A101D1B079};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>

Basically, it’s saying that it’s a workflow project and it’s a C# project.  If you’re using VB, create a new custom workflow activity then open the project file in notepad and you should see a different ProjectTypeGuids node that you can use.

The second part is an import statement that just goes inside of the root <Project> node.  It is:

<Import Project="$(MSBuildExtensionsPath)\Microsoft\Windows Workflow Foundation\v3.0\Workflow.Targets" />

Adding these two entries to your project file makes the workflow extensions work in Visual Studio and can make your custom activity work – even when you started with a standard class library.