What are circular references in C#?

The circular reference problem in C# causes a lock condition in two independent components/classes. This problem occurs when two or more parts of the program depend upon each other, making their resources unusable.

The lock condition

Example

Let's see how this circular reference problem arises through an example:

public class Pet{
    Dog petName;
}
public class Dog{
    Pet petName;
}
class HelloWorld
{   
    static void Main()
    {
        Dog tom = new Dog();
        System.Console.WriteLine("Hello, World!");
    }
}

Explanation

Line 1–6: We have a public class called Pet and another class named Dog. The principle of composition can be seen in both classes as Pet has a data member petname of type Dog and Dog has a data member dogname of type Pet. Presence of circular reference problem.

Illustration of the example

Solution

The introduction of an interface can solve this problem:

public interface Ibridge{
}
public class Pet{
    Ibridge interface_common;
}
public class Dog:Ibridge{
    Pet petName;
}
class HelloWorld
{   
    static void Main()
    {
        Dog tom = new Dog();
        tom.setDogName("Tim");
        System.Console.WriteLine("Hello, World!");
    }
}

As an interface is introduced, now the classes do not depend directly on each other and have a shared resource that they can utilize to avoid the circular reference problem.

Dependency graph

The dependency graph shows that Dog now depends upon Pet and Ibridge. Meanwhile, Pet also depends on Ibridge. This breaks the circular dependency and resolves the lock condition.

Conclusion

Circular references are logical errors that can obstruct data flow within a program. By introducing interfaces, we can avoid this error in our code.

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