Factorial Number Program in C#

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace Factorial

{

    class Program

    {

        // Using Recursion

        public static long GetFactorialUsingRecursion(int num)

        {

            if (num == 0)

            {

                return 1;

            }

            return num * GetFactorialUsingRecursion(num - 1);

        }

        // Using For Loop

        public static long GetFactorialUsingForLoop(int num)

        {

            long fact = 1;

            for (int i = 1; i <= num; i++)

            {

                fact = fact * i;

            }

            return fact;

        }

        // Using While Loop

        public static long GetFactorialUsingWhileLoop1(int num)

        {

            int count = 1;

            long fact = 1;

            while (count <= num)

            {

                fact = fact * count;

                count++;

            }

            return fact;

        }

        // Using While Loop

        public static long GetFactorialUsingWhileLoop2(int num)

        {

            long fact = 1;

            while (num > 1)

            {

                fact = num * fact;

                num = num - 1;

            }

            return fact;

        }

        static void Main(string[] args)

        {

            int num = 5;

            Console.WriteLine("Using Recursion - {0} factorial is {1}", num, GetFactorialUsingRecursion(num));

            Console.WriteLine("Using For Loop - {0} factorial is {1}", num, GetFactorialUsingForLoop(num));

            Console.WriteLine("Using While Loop 1 - {0} factorial is {1}", num, GetFactorialUsingWhileLoop1(num));

            Console.WriteLine("Using While Loop 2 - {0} factorial is {1}", num, GetFactorialUsingWhileLoop2(num));

            Console.ReadLine();

        }

    }

}

Output: