I am new to ASP.NET, and I am working on a project which contains two C# and one VB.NET projects.
I want to put it all in a single project. How would I do it?
You can't mix different languages within a same project - but it's simple enough to have a class library written in C# that's called by VB or vice versa.
It's possible that you could write your ASP.NET pages in one language and have other code written in another language in the same project - but I would personally try to keep the presentation part of the code in one project and the logic in another, with each project only using a single language.