Circular Dependency in Two Projects in C#

Question

I have two projects in a solution named ProjectA (ConsoleApplication) and ProjectB (ClassLibrary). ProjectA has a reference to ProjectB. Generally speaking, ProjectA calls a

Answer 1

It is actually possible to create projects that have circular dependencies that compile successfully but I strongly recommend against it. Instead, organize your projects so that they have an acyclic dependency graph.

There are a number of ways to solve this problem, several of which have been mentioned in other answers. One not yet posted is to eliminate the dependency between project A and project B entirely, and create a third project, C, that defines the interfaces that A and B communicate over. That is:

namespace C
{
    public interface IFoo { void Frob(); }
    public interface IBar { void Qux(); }
}

And then make projects A and B reference project C, and make their classes implement IFoo, IBar, and so on. When a method in project A needs to call Frob on an object in project B, it does so by obtaining an IFoo, rather than obtaining some class in B.

Does that make sense?