Circular dependency on injection within same class library

Question

I have below classes and implementation inside same class library

public interface IA
    {

    }

    public class A : IA
    {
        private IB _ib;

        public A(IB ib)
        {
            _ib = ib;
        }
    }

    public interface IB
    {

    }

    public class B : IB
    {
        private IA _ia;

        public B(IA ia)
        {
            ia = _ia;
        }
    }

My question is when, either IA or IB, gets instantiated, will it create any circular dependency when performing dependency injection? If so, how can this be resolved?

Answer 1

Your code will have circular dependency and will throw exception at runtime. You need to refactor your code so that A and B do not have dependencies on each other. You will need to extract a new interface (IC) out of either A or B and refactor your code to something like the following:

public interface IA {
}
public class A : IA {
  IC _c;
  public A(IC c) {
    _c = c;
  }
}

public interface IB {
}
public class B : IB {
  IA _a;
  IC _c;
  public B(IA a, IC c) {
    _a = a;
    _c = c;
  }
}

public interface IC {
}
public class C : IC {
}

See Circular Dependency in constructors and Dependency Injection on how to refactor your classes to remove circular references