Find the factorial through ForEach condition using switch case

Find the factorial through ForEach condition using switch case

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace ConsoleApplication1

{

    class fact

    {

        public static void Main()

        {

            int a, f = 1, ch;

            int[] b = new int[1];

            Console.WriteLine("Enter any number=");

            a = Int32.Parse(Console.ReadLine());

            Console.WriteLine("you can calculate factorial using:");

            Console.WriteLine("1- for loop");

            Console.WriteLine("2- while loop");

            Console.WriteLine("3- do-while loop");

            Console.WriteLine("4- for each loop");

            Console.WriteLine("\nenter your choice");

            ch = Int32.Parse(Console.ReadLine());

            switch (ch)

            {

                case 1: for (int i = 1; i <= a; i++)

                        f = f * i;

                    Console.WriteLine("factorial is=" + f);

                    Console.ReadLine();

                    break;

                case 2: while (a > 0)

                    {

                        f = f * a;

                        a = a - 1;

                    }

                    Console.WriteLine("factorial is=" + f);

                    Console.ReadLine();

                    break;

                case 3: do

                    {

                        f = f * a;

                        a = a - 1;

                    }

                    while (a > 0);

                    Console.WriteLine("the factorial is" + f);

                    Console.ReadLine();

                    break;

                case 4:

                    while (a > 0)

                    {

                        f = f * a;

                        a = a - 1;

                    }

                    b[0] = f;

                    foreach (int i in b)

                        Console.WriteLine("factorial is=" + i);

                    Console.ReadLine();

                    break;

                default: Console.WriteLine("wrong choice");

                    break;

            }

        }

    }

}

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