title: Configure Visual Studio 2012 to use Mono's C# compiler instead of the default csc.exe
body: <p>I work in a game engine called Unity3D whose scripting system runs on Mono. By default Unity uses a modified version of Mono to develop/compile script. I am in the process of setting up my Visual Studio to better work with Unity projects and its various gotchas with regards to .NET.</p>
  
  <p>I am currently stuck trying to configure Visual Studio to handle compilation of my various assemblies. Unity uses a modified version of an old Mono compiler, and as such I <em>cannot</em> use the default csc.exe to build assemblies.</p>
  
  <p>My ideal solution would be for Visual Studios's <strong>Build Solution</strong> option to process my projects with a compiler I point it to, perhaps through configuring the MSBuild (.csproj) file? Falling short of this is there another way I can build from <strong>within Visual Studio</strong> using Mono's mcs/gmcs compiler?</p>