Using Visual Studio 2017 and attempting to add a reference to a project you receive an error stating “The operation could not be completed”.
It seems that to bring up the Add Reference dialog in Visual Studio 2017 the Microsoft.VisualStudio.Shell.Interop.11.0.dll needs to be regsitered in the GAC. You can follow these steps to register this assembly in the GAC:
Open the Develop Command Prompt for VS2017 (ensure you run the as administrator otherwise the GAC registration may fail)
Change the current directory to the PublicAssemblies folder for your Visual Studio 2017 installation. Mine was:
C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\Common7\IDE\PublicAssemblies
Note: this path will be different for different versions of Visual Studio (e.g. you may find your path is C:\Program Files\Microsoft Visual Studio\2017\Community\Common7\IDE\PublicAssemblies)
Run the following command to register the assembly in the GAC:
gacutil -i Microsoft.VisualStudio.Shell.Interop.11.0.dll
Now restart VS2017 and try to add a reference to your project again and you should see the Add Reference dialog appear.