Do app code support only to put one kind of file?

Do app code support only to put one kind of file, i mean either c# class or vb class? Because if i put both sort of file and create an object then, application throws e开发者_运维技巧rror. How can i make App code compatible with both.

Within a single assembly or project you can only have one kind of source code, although you may reference multiple assemblies (of different languages) within the same project.