Somehow you disagree with your C # / VB compilers. Your project files are trying to pass a property that we added to the newer version of the compilers, but you are still using an older version of the compilers. It is unclear, based on your description, if all the projects that were broken, or just some. Things I would check:
- If only some projects are not created, make sure that you do not have our NuGet packages for the compiler installed, but you have not completed the recovery.
- If you had the experimental version of Roslyn compilers installed that you forgot about, make sure that it is still installed.
- If all projects are not created (including you are building a completely new one), make sure that there is nothing strange in Extension Manager. If nothing happens, repair Visual Studio.
source share