I have an MSBuild command line that can build an entire solution. It looks something like this:
msbuild SomeSolution.sln /p:Configuration:CustomDebug;Platform=Our
Invoke MSBuild on the project file instead of the solution file (ref.msbuild /?)
msbuild /?
msbuild SomeDotNetProject\SomeDotNetProject.csproj /p:Configuration:CustomDebug;Platform=OurPlatform /nodeReuse:false /maxcpucount:4 /t:Build