Based on what I know about MsBuild this is not possible by "standard" way. But here are the options you can achieve it: 1) Pass property values in MSBuild command line for building your root solution: msbuild mySolution.sln /t:Build /p:Configuration=...;Platform=...;DeploymentBranch=...;AppRoot=...
2) In your refproj.csproj, you can import main.csproj . but keep in mind the "relativeness" of your paths and that main.csproj might override your refproj.csproj properties and targets.