Factorial in C#

 Factorial of a number is obtained from the result of multiplying a series of descending natural numbers. Factorial of n is the product of all positive descending integers. Factorial of n is denoted by n!. 
Example:
    5! = 5*4*3*2*1 = 120  
6! = 6*5*4*3*2*1 = 720
Here, 5! is pronounced as "5 factorial", it is also called "5 bang" or "5 shriek".
The factorial is normally used in Combinations and Permutations (mathematics).

3 Different ways to calculate factorial in C#  

Using For Loop: 
    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
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();
         }
    }
}
Output:
Enter the Number: 5
Factorial of Given Number is: 120

 Using Recursion: 
    class Program
    {
        static void Main(string[] args)
        {
                int number;
                Console.WriteLine("Enter the Number");
                number = int.Parse(Console.ReadLine());
                double fact;
                fact = factorial_Recursion(number);
                Console.WriteLine("\nFactorial of Given Number is: " + fact);
                Console.ReadLine();
        }
        public static double factorial_Recursion(int number)
        {
            if (number == 1)
                return 1;
            else
                return number * factorial_Recursion(number - 1);
        }
    }
Output:
Enter the Number: 8
Factorial of Given Number is: 40320

 Using While Loop: 
    class Program
    {
        static void Main(string[] args)
        {
                int number;
                Console.WriteLine("Enter the Number");
                number = int.Parse(Console.ReadLine());
                double fact;
                fact = factorial_Recursion(number);
                Console.WriteLine("\nFactorial of Given Number is: " + fact);
                Console.ReadLine();
        }
        public static double factorial_Recursion(int number)
        {
            if (number == 1)
                return 1;
            else
                return number * factorial_Recursion(number - 1);
        }
    }
Output:
Enter the Number: 4
Factorial of Given Number is: 24


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