在c#中使用递归计算阶乘

我知道如何使用循环计算阶乘。下面是循环的代码，但我得到一个错误，而做它的递归。下面是两个代码示例。我该如何解决这个问题?

namespace factorial
{
    class Program
    {
        static void Main(string[] args)
        {
            int i, number, fact;
            Console.WriteLine("Enter the Number");
            number = int.Parse(Console.ReadLine());
            fact = number;
            for (i = number - 1; i >= 1; i--)
            {
                fact = fact * i;
            }
            Console.WriteLine("'nFactorial of Given Number is: "+fact);
            Console.ReadLine();
        }
    }
}

使用递归的阶乘:

是否有什么地方我错了?我什么时候用递归计算它?

阶乘使用循环:

public double factorial_Recursion(int number)
{
    if (number == 1)
        return 1;
    else
        return number * factorial_recursion(number - 1);
}
public double factorial_WhileLoop(int number)
{
    double result = 1;
    while (number != 1)
    {
        result = result * number;
    }
    return result;
}

factorial_Recursion is the method name.
factorial_recursion is the call.

namespace Testing
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(factorial_Recursion(5));
            Console.WriteLine("press any Key");
            Console.ReadLine();
        }
        public static double factorial_Recursion(int number)
        {
            if (number == 1)
                return 1;
            else
                return number*factorial_Recursion(number - 1);
        }