Context: Stack Overflow #50479716 (accepted answer, 37 votes): dotnet core projects get skipped from SonarQube analysis with the warning "The following projects do not have a valid ProjectGuid and were not built using a valid solution (.sln) thus will be skipped from analysis". The default dotnet core project template does not include a ProjectGuid tag, so SonarQube skips those projects.

[accepted answer]: default dotnet core .csproj templates ship without a ProjectGuid element, and SonarQube requires one. Fix it in each .csproj by adding a ProjectGuid element containing a fresh GUID, nested inside a PropertyGroup element of the file. Generate a new GUID per project (Visual Studio has Tools > Create GUID, PowerShell has New-Guid, mac and linux have uuidgen). Dont copy one GUID across projects; duplicates make the analysis treat them as the same project. Rebuild, re-run the scanner, and the "no valid ProjectGuid" warning goes away.