title: Using .NET 4.5 code in Unity 5
body: <p>I am working on a game using Unity3D version 5. The game should use strict business rules already programmed in a C# .NET4.5 engine. Using Xamarin/Mono, we hope to make this usable on windows, android, others...</p>
  
  <p>I tried building the engine into a dll and use it as a managed plugin in Unity. But Unity uses an old version of Mono to compile the whole game and refuses to use .NET 4.5 dlls.</p>
  
  <p>I really need to use this code, I looked into downgrading it to .NET 3.5 but it is not an acceptable solution given the work already done on the engine.</p>
  
  <p>Concerning android, I think to use Xamarin to get native android code and use it as a native plugin in Unity. Now I need a solution for Windows. I am looking into ways to use the C# code in C++ to make an unmanaged dll but I am struggling understanding which way is applicable here between COM interop, C++/CLI or other methods.</p>
  
  <p>Does any one knows a way to include code from .NET 4.5 in Unity with no/little effort ?</p>