Random Number generator that doesn't repeat itself

Question

I'm trying to create a random number generator between 1 and 500 that does not repeat itself. I made an array to keep track of if a generated number has been used but it doesn't seem to be working

if (drawnTF[num] == false)
            {
                labels[labelNum].Visible = false;
                txtLatestDrawnNum.Text = "Latest Drawn Number: " + latestDrawnNum.ToString("000");
                drawnTF[num] = true;
            }
            else
            {
                while (drawnTF[num] == true)
                {
                    num = random.Next(0, 499);
                    if (drawnTF[num] == false)
                    {
                        labelNum = 499 - num;
                        labels[labelNum].Visible = false;
                        txtLatestDrawnNum.Text = "Latest Drawn Number: " + latestDrawnNum.ToString("000");
                        drawnTF[num] = true;
                    }
                }
            }

Answer 1

You can try to put 500 numbers in an list and do a next(0,values.Length). Each time you pick a random number you remove it from that list. This way you will always have different numbers.