In the same project in Visual Studio? You can't. A project can target
only one language (as you need to run a compiler against it and all the code
items have to be able to be recognized by the one compiler).
Now, you can compile C++ code and C# code into the same ^assembly^, but
you would have to more than likely use the command line compilers to do
this. You would have two projects, one C#, and one C++, and then compile to
netmodules. Then, you would use al.exe (the assembly linker) to compile the
modules into an assembly.
Of course, you can have a C# project and a C++ project in the same
^solution^ and have your C++ code create managed assemblies, which you
access in your C# project, or vice versa.
