Error while loading project: Attribute Include is unrecognized
I found the error... there was a merge conflict with a Reference-Tag with no close-tag because it was deleted while merging.
when you build the csproj file with MSBuild you get the line-number on which the error occurs. This is unfortunately not visible in VisualStudio.
- Open the Develop Commnand Prompt for Visual Studio
- Navigate to the folder which contains the csproj file
- Run MSBuild
In the error, it contains the line-number with the error in the csproj file. This helped me fixing the file after a GIT merge