Does "new Random (x)" always generate the same numbers?

I try to get a unique random number, but always get the same number every time I run the code. I will get 14 first and then 6, but my list for storing all used numbers does not seem to work. When using 14 manual jobs, but when I add randInt, it does not work.

const int numCards = 32;
        List<int> usedCards = new List<int>();
        int randInt = 0;
        Random rand = new Random(numCards);
        usedCards.Add(14);
        do
        {

            randInt = rand.Next(0, numCards);
            MessageBox.Show(randInt.ToString(), "End Game", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);

        }
        while (usedCards.Contains(randInt));

        usedCards.Add(randInt);