Question

That’s very simple question I believe. Could anybody explain why this code outputs 1000, not 1050

public class Program
    {
        public static void Main()
        {
            Bus b = new Bus(1000);
            ((Car)b).IncreaseVolume(50);
            Console.WriteLine(b.GetVolume());
        }
    }

    public interface Car
    {
        int GetVolume();
        void IncreaseVolume(int amount);
    }

    public struct Bus : Car
    {
        private int volume;

        public Bus(int volume)
        {
            this.volume = volume;
        }

        public int GetVolume()
        {
            return volume;
        }

        public void IncreaseVolume(int amount)
        {
            volume += amount;
        }
    }
}

Answer 1

Casting a value type (struct) to an interface boxes the value. So you’re invoking the method on the boxed copy of the value, not on the value itself.