Why are Visual Studio projects restricted to a single language?

Question

This is question is inspired by the question: In what areas does F# make "absolute no sense in using"?

In theory, it should be possible to use any .NET supported language in a single project. Since every thing should be compiled into IL code, then linked into a single assembly.

Some benefits would include the ability to use say F# for one class, where F# is more suited to implement it's function, and C# for another.

Is there some technical limitation I'm overlooking that prevents this sort of setup?

Answer 1

A project is restricted to a single language because, under the hood, a project is not much more than an MSBuild script which calls one of the command-line compilers to produce an assembly from the various source code files "contained" in the project folder. There is a different compiler for each language (CSC.exe is for example the one for C#), and what each project has to do to turn its "contained" source code into an assembly differs with each language.

To allow multiple languages to be compiled into a single assembly, the project would basically have to produce an assembly for each language, then IL-Merge them. This is costly, requires complex automation and project file code generation, and in most circumstances it's a pretty fringe need, so the VS team simply didn't build it in.

Answer 2

While projects are restricted to a single language, a solution is not... and solutions can contain multiple projects.