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Question

I have a project (project B) that has a reference to another project (project C), and uses some methods from this project. Now, I have a third project (project A) which needs to use only project B methods (and these methods use project A methods) - Project A uses project C but not directly.

1. Do I need to add a reference to project C or just to project B?
2. If I'll add a .dll reference, can I just add reference to project B?

Answer 1

1. Do I need to add a reference to project C or just to project B?

Just B is enough. If you are adding project reference in Visual Studio, adding project reference of B is enough. At compile time, dlls of both project (B and C) will be copied to executable path of A

2. If I'll add a .dll reference, can I just add reference to project B?

In that case you will only be required to add reference to the project B dll, but project C 's dll should be in the executable folder as well, since project B depends on it.

In both cases you don't have to reference project C explicitly, since there will be no direct calls to project C from Project A. But remember in both cases you will end up with the Project C dll in your Project A executable.

You may see: Managing Project References - MSDN

Seeing @David's comment , you can't have circular reference in your projects. Project A using methods of Project B and Project B using methods of Project A, you will not be able to compile this code. You need to redesign your code and have hierarchy in your projects like A -> B -> C

See: Why are circular references in Visual Studio a bad practice?

Answer 2

You will most likely need both, since B depends on C . If there is a method signature exposing a type of C , you definitely will need the reference to make it compile. Else, you would probably need it at runtime.

If possible, always add it as reference, since IntelliSense will notice the project reference and will notice method changes before you compile.