HOW TO BUILD A WEB PROJECT INTO MULTIPLE .DLL?

I have a 开发者_如何学CWeb Project that has three Folder(A,B,C) that contains .cs files. There will be one .DLL Build by VS by default. but now I want to Build the project into multiple .dll files(A.dll, B.dll,C.dll), Any one tell me how can I make it?

Separate them into 3 projects A,B & C (still in same solution) and then add Project Reference to the main Web Project