Question

Possible Duplicate:
Post-increment Operator Overloading
Why are Postfix ++/— categorized as primary Operators in C#?

I saw that I can overload the ++ and -- operators.
Usually you use these operators by 2 ways. Pre and post increment/deccrement an int
Example:

int b = 2; 
//if i write this
Console.WriteLine(++b); //it outputs 3
//or if i write this
Console.WriteLine(b++); //outpusts 2

But the situation is a bit different when it comes to operator overloading:

    class Fly
    {
        private string Status { get; set; }

        public Fly()
        {
            Status = "landed";
        }

        public override string ToString()
        {
            return "This fly is " + Status;
        }

        public static Fly operator ++(Fly fly)
        {
            fly.Status = "flying";
            return fly;
        }
    }


    static void Main(string[] args)
    {
        Fly foo = new Fly();

        Console.WriteLine(foo++); //outputs flying and should be landed
        //why do these 2 output the same?
        Console.WriteLine(++foo); //outputs flying
    }

My question is why do these two last lines output the same thing? And more specifically why does the first line(of the two) output flying?

---

Solutions is to change the operator overload to:

        public static Fly operator ++(Fly fly)
        {
            Fly result = new Fly {Status = "flying"};
            return result;
        }

Answer 1

The difference between prefix and postfix ++ is that the value of foo++ is the value of foo before calling the ++ operator, whereas ++foo is the value that the ++ operator returned. In your example these two values are the same since the ++ operator returns the original fly reference. If instead it returned a new “flying” Fly then you would see the difference you expect.