C# - Circular Reference and cannot see Namespace

Question

I have a solution with 2 projects.

One, Raven, is a simple base that provides data for the second project, PPather, to do stuff with. The second project depends on the first to compile so to build it, I add a reference to Raven. All works well so far.

Now I want Raven to launch PPather. But it can't see the PPather naemspace so I can't. All efforts to resolve this lead to circular reference errors.

Anyone know how I can get Raven to see the namespace of the PPather project that depends on it?

Answer 1

You can't - there is no way to reference assemblies in a circular manner like you want to do. Most likely you have not properly designed these assemblies if you need to create a circular reference.

Your first assembly is a dependency so there should not be any code in there that knows about anything other than its dependencies. Once your assemblies become "smart" and begin to have knowledge of anything outside their own dependencies you will begin to have serious maintenance and scalability headaches. I would look into reorganizing your code in such a manner that you do not need to create the circular reference.

Answer 2

There is a ton of stuff you can do to achieve this if you are not willing to combine them into one component. All basically strive to either invert one of the dependencies or to create a third component on which both depend.

It seems that Raven is the starting point, so one possible solution is to create a base class or interface in the PPather component which reflects the feature set that PPather seeks in Raven. Raven can then implement this base class and then include a "this"-pointer when instantiating/invoking PPather. PPather will expect a pointer to the base class (or interface) in his own assembly, and therefore will never "know of" Raven except through his own abstraction. Therefore, the circular dependency will be broken (by means of dependency injection).

Answer 3

As Andrew says, you can't and it doesn't make much sense that you'd want to.

Basically, do one of the following:

• Merge the assemblies; if they really inter-depend tightly, then they really should not be separate in the first place.

• Re-design the assemblies so that they do not directly depend on each other in both directions; for instance, make assembly A depend on an interface defined in assembly C, and have assembly B implement this interface (both depend on C).

Answer 4

By Launching PPanther, do you mean that PPanther is an executable that you need to run?

In this case, you can use Process.Start to launch PPanther?

Answer 5

It is fortunate that you can not add circular references - because they cause maintenance nightmares.

You want Raven to launch PPather? Is PPather as console/windows application? Use Process.Start to do that (and store the location of PPather in the registry somewhere).

Alternatively create interfaces for the classes that you need out of PPather - and make the classes in PPather implement those interfaces.

interface IPPatherInterface // Inside of Raven.
{
    void Foo();
}

class PPatherClass : IPPatherInterface // Inside of PPather
{
    // ...
}

class SomeRavenClass // Static maybe? Inside of Raven
{
    void SupplyPPatherClass(IPPatherInterface item) { ... }
}

You now have a way for PPather to supply that interface's implementation to Raven.

Answer 6

Branch out the calsses in raven that Panther needs to use from raven to a different assembly, and have both panther and Raven reference them.

Although to be honest if Raven needs to run panther then i think your design is a bit Off. you should break off your code into something more manageable.