c# - What's the difference between X = X++; vs X++;?

Question

Have you ever tried this before?

static void Main(string[] args)
{
    int x = 10;
    x = x++;
    Console.WriteLine(x);
}

Output: 10.

but for

static void Main(string[] args)
{
    int x = 10;
    x++;
    Console.WriteLine(x);
}

Output: 11.

Could anyone explain why this?

Answer 1

X++ will increment the value, but then return its old value.

So in this case:

static void Main(string[] args)
{
    int x = 10;
    x = x++;
    Console.WriteLine(x);
}

You have X at 11 just for a moment, then it gets back to 10 because 10 is the return value of (x++).

You could instead do this for the same result:

static int plusplus(ref int x)
{
  int xOld = x;
  x++;
  return xOld;
}

static void Main(string[] args)
{
    int x = 10;
    x = plusplus(x);
    Console.WriteLine(x);
}

It is also worth mentioning that you would have your expected result of 11 if you would have done:

static void Main(string[] args)
{
    int x = 10;
    x = ++x;
    Console.WriteLine(x);
}