Hi Einar,

So the best or most common way is to add the separate/reuasable projects to the new solution and add the nessesary references this way. If I understand things correctly all the projects get compiled and built at the same time.

That's generally what I do. Keep in mind that you can (and should) define project dependencies and build order at the solution level. For example, any composite/user control projects rely on your subclassed controls, other form classes might rely on composite/user controls, etc. Again, mapping out ahead of time your project structure can go a long way towards managing the entire process.

Are there any circumstances when you don't want to add the project to the solution and just add reference to the DLL file?

I can't think of any, off the top of my head. (Except for instances where you have a DLL from a third party, but no project exists - in that case, you don't have much choice).

If I'm adding a project reference, there's always the chance I may need to modify (or at least view) the code in that project being referenced. By adding it to the solution, it makes it easier to pull up, as opposed to closing the current project/solution and opening the other one.

Again, you need to make sure you've defined your dependencies correctly.

That's what has generally worked for me.

Kevin