Unknown solution item type: {42C0BBD9-55CE-4FC1-8D90-A7348ABAFB23}

Question

I am trying to open a project in Monodevelop (3.0.5, with MonoMac add-in enabled) on Mac Mavericks.

I get this error:

MonoDevelop.Projects.Formats.MSBuild.UnknownSolutionItemTypeException: Unknown solution item type: {42C0BBD9-55CE-4FC1-8D90-A7348ABAFB23};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}
  at MonoDevelop.Projects.Formats.MSBuild.MSBuildProjectHandler.CreateSolutionItem (IProgressMonitor monitor, MonoDevelop.Projects.Formats.MSBuild.MSBuildProject p, System.String fileName, System.String language, System.String typeGuids, System.String itemType, System.Type itemClass) [0x00143] in /Users/builder/data/lanes/monodevelop-lion-monodevelop-3.0-series/e159cf08/source/monodevelop/main/src/core/MonoDevelop.Core/MonoDevelop.Projects.Formats.MSBuild/MSBuildProjectHandler.cs:369

The most relevant part is probably this one:

Unknown solution item type: {42C0BBD9-55CE-4FC1-8D90-A7348ABAFB23};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}

These UUIDs can be found in the <ProjectTypeGuids> of the .csproj file I try to open.

• FAE04EC0-301F-11D3-BF4B-00C04F79EFBC is the UUID for C# projects,
• 42C0BBD9-55CE-4FC1-8D90-A7348ABAFB23 is the UUID for MonoMac projects.

I can open other C# projects normally, so I guess this is a problem with Monomac?

Monodevelop has the MonoMac add-in enabled. I tried to compile MonoMac from source but the DLL it generates can't be loaded as an add-in (ZipException).

Answer 1

The solution was to remove the following line from the .csproj altogether:

<ProjectTypeGuids>{42C0BBD9-55CE-4FC1-8D90-A7348ABAFB23};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>

The project can then be loaded normally in Monodevelop.

Answer 2

I had this error with the build-in mono dev of last few version of Unity on OSX.

To solve it: Add-in manager -> Language bindings -> Enable C# binding

Answer 3

I experienced a similar issue using Visual Studio for MacOS. Running a git diff on the .csproj revealed some stray non-printable Unicode characters had been inserted at the beginning of the file:

<U+FEFF><U+FEFF><?xml version="1.0" encoding="utf-8"?>

I resolved the issue by manually deleting and retyping the <?xml portion.