使用循环计算C#中的阶乘

namespace factorials
{
    class Program
    {
        static void Main(string[] args)
        {
            int number;

            do
            {
                Console.WriteLine("What non-negative integer do you want to factorial?");
                while (!int.TryParse(Console.ReadLine(),out number))
                    Console.WriteLine("Please enter a whole number only");
                calculate(ref number);
            } while (number >= 0);
            Console.WriteLine("Please enter a non-negative number");

        }
        static void calculate(ref int number)
        {
            int factorial;
            int counter;

            for (counter = number; counter <= number; counter++)
            {
                factorial = number * number;
                Console.WriteLine("The factorial of {0} is {1}",number,factorial);
            }

    }
    }
    }

现在它只是给了我数字的平方,而不是它们的阶乘.如何使其作为输入重复次数,从而导致因子？

此外,我不确定是否有必要将程序仅限制为非负整数,但如果我想要那个部分只是在那里结束程序而不是循环回到开头.