VS2013 C# projects in VS2015: Will they use the Roslyn compiler?

Question

Not entirely certain that this is even a valid question, however if I use VS2015 to open a solution that was originally created and maintained with VS2013, will it be compiled using the Roslyn compiler platform whenever built (within VS2015)?

The solution consists of WPF applications, Console applications, Web Applications, Windows Service applications and of course class libraries - so a good all round selection of options.

If this is not the case, how should I enable the Roslyn compiler for these projects?

Thanks.

Answer 1

If you open in VS2015, it will always use the Roslyn compiler to compile, regardless of the language version switch.

Using the /langversion switch simply tells the Roslyn compiler not to allow new features - it doesn't cause an older compiler to be used.