Question

Let me have two very basic objects like:

public class View
{
    public View(Controller controller)
    {
        // Use the model exposed by the controller here
    }
}

public class Controller
{
    private readonly IView view;

    public Controller()
    {
        this.view = new View(this);
    }

    public Controller(View v)
    {
        this.view = v;
    }
}

Later I decide to inject View object into the Controller via DI but there I have a cyclic dependency (i.e. I can’t use var ctrl = new Controller(new View(ctrl));). How would you go about injectin the dependency in this case?

Answer 1

The most common solution is to use a dependency property to solve circular dependencies. i.e. create a new property in one of the classes and let the IoC container assign it.

If you are using Unity you should add [Dependency] to that property.

A sidenote: A View should not have a dependency to a controller. It should not be aware of it at all.

Update in reply to comment

You can’t. That’s the problem with circular dependencies. The only other solution is to use composition. That is to break out the common functionality into a separate class and include it in both the controller and the view.