<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">

  <Import Project="Proj1/Proj1.proj"/>
  <Import Project="Proj2/Proj2.proj"/>

  <Target Name="Build">
    <Message Text="%(Compile.FullPath)"/>
  </Target>
</Project>

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <ItemGroup>
    <Compile Include="Test#.cs"/>
  </ItemGroup>
</Project>

C:usersmpflugDesktopmsbuildtestTest1.cs
C:usersmpflugDesktopmsbuildtestTest2.cs

C:usersmpflugDesktopmsbuildtestProj1Test1.cs
C:usersmpflugDesktopmsbuildtestProj2Test2.cs