Random class

Try this:

class MyRandom
    {
        private List<int> numbers = new List<int>();
        private Random random;
        public void Initialize(int min, int max)
        {
      numbers.Clear();
            random = new Random();
            for (var i = min; i <= max; i++)
            {
                numbers.Add(i);
            }
        }

        public int GetNext()
        {
            var index = random.Next(0, numbers.Count);
            var result = numbers[index];
            numbers.RemoveAt(index);
            return result;
        }
    }

//USAGE
MyRandom rand = new MyRandom();
            rand.Initialize(1,600);
            Console.WriteLine(rand.GetNext());