Hi, I have two project solutions! Project1 and Project2. I want to merge these two, so there will be single solution Project1? I tried my best but unable to do so! How to do it without affecting my program, resources, assemblies etc.?

P.S : I m using VS2010

In Solution Explorer, right click the solution name and select:
Add -> Existing Project

Browse to your existing project and add it.
Remember to add the reference from the sub-project to the main project.
...do it in the "project" tab under the Add References dialog box.

Alright I have merged but I still see two project in solution explorer.
How to make them as one? Do I need to write code all over again.

You'd have to merge the source files manually and rebuild, but what's wrong with having two projects in the solution? You can reference one from the other (there's a Projects tab in the add reference dialog) if sharing is necessary.

My thought was that you just needed to have them compiled at the sme time bacuse you're working on both sets of code.

Can they be separated in different chunks-of-functionality so that one can stay in its own DLL?