break

            int numOne = 17;
            int numTwo = 2;
            while (numTwo <= numOne - 1)
            {
                if (numOne % numTwo == 0)
                {
                    Console.WriteLine("Not a Prime Number");
                    break;
                }
                numTwo++;
            }
            if (numTwo == numOne)
            {
                Console.WriteLine("Prime Number");
            }