Contravariance with in keyword in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of contravariant interface assignment

What is the output of this C# program using contravariance with the in keyword?

C Sharp (C#)

using System;

interface IContravariant<in T>
{
    void Show(T item);
}

class Printer : IContravariant<object>
{
    public void Show(object item) => Console.WriteLine(item);
}

class Program
{
    static void Main()
    {
        IContravariant<string> printer = new Printer();
        printer.Show("Hello World");
    }
}

A Hello World

B No output

C Runtime error: InvalidCastException

D Compile-time error: Cannot convert IContravariant<object> to IContravariant<string>

💡 Hint

Remember that contravariance allows assignment from a less derived to a more derived generic type when using the in keyword.

The interface IContravariant is contravariant in T because of the in keyword. This means you can assign an IContravariant