Sonargraph uses MSBuild to retrieve configuration info for C# projects. This specific error can be resolved by removing the following lines from the .csproj file as described on stackoverflow:
<PropertyGroup>
<VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">10.0</VisualStudioVersion>
<VSToolsPath Condition="'$(VSToolsPath)' == ''">
$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
</PropertyGroup>
