Add

            public void Add()
            {
                int RandNo = 0;
                if (Rear < MaxSize - 1)
                {
                    RandNo = Rnd.Next(0, 26);
                    Rear++;
                    Contents[Rear] = Convert.ToChar(65 + RandNo).ToString();
                }
            }

Generates a random number and adds it on to the queue before adding one to 'Rear'. The if loop finishes once the 'Rear' becomes equal to 'maxsize' minus 1. Note if the queue is full then then this method essentially does nothing.