A tiny utility to set the LangVersion property of all *.csprojs in a folder
Download the latest release from here.
Then run LangVersionFixer <folder-with-csprojs> <lang-version-number>.
LangVersionFixer "C:\Code\AwesomeProject" 5 - Will set LangVersion to 5 for all *.csproj under C:\Code\AwesomeProject.