‘ProjectTypeGuids’ node in VS project files

I wanted to create a WPF resource dictionary and put it in a separate assembly for a certain purpose. I started up by creating a regular class library and was about to add a new item to it when I was puzzled – I couldn’t find a proper template anywhere in the UI the Visual Studio provided to me. It was absent on the ‘New File’ dialog and it wasn’t there on the context menu either.

However, I knew it should be there, I’ve tried another project that was specifically created using one of the WPF templates and the items were there:

I tried adding WPF assemblies to my class library references (PresentationCore, PresentationFramework, System.Xaml, WindowsBase) but it didn’t make Visual Studio realize I need WPF specific items. I didn’t find a way to set it within a standard project’s settings dialog.

Then I compared the two project files (.csproj) and the only line that was interesting was:

<PropertyGroup>
  ...
  <ProjectTypeGuids>{60dc8134-eba5-43b8-bcc9-bb4bc16c2548};
         {FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
  ...
</PropertyGroup>

On a regular class library project the ‘ProjectTypeGuids’ node was missing at all. It didn’t take long to find what those mysterious GUID’s are about: List of known project type Guids. So the first one says it’s a WPF project and the second one says it’s a C# project.

Adding the line to the project file did the trick and I was just left wondering why it’s such a bad idea to provide appropriate UI to control project types. Not a big deal though…