Validating *.sln and *.csproj files

I need to modify both *.sln and *.csproj files, especially all files added into VS, and properties.

Are there validators for both files, which validate if all files are valid and can be loaded and are working within Visual studio. Manually load them one by one into VS, and check every property are impractical due to the number of files.

Ideally free validators?

Thanks in advance.