Looping constructs

Looping constructs

v  The following loop constructs are supported by C#:

Ø  The while loop

Ø  The do…while loop

Ø  The for loop

Ø  foreach loop

The while loop

The while statement executes a statement or a block of statements until a specified expression evaluates to false.

It should be used if number of iteration is not known

Example

using System;

namespace while_loop

{

    class Program

    {

        static void Main(string[] args)

        {

            Console.WriteLine("Enter a Number");

            int numb = int.Parse(Console.ReadLine());

            int reverse = 0;

            while (numb > 0)

            {

                int rem = numb % 10;

                reverse = (reverse * 10) + rem;

                numb = numb / 10;

            }

            Console.WriteLine("Reverse number={0}", reverse);

            Console.ReadLine();

        }

    }

}

The do…while loop

Unlike while loops, which test the loop condition at the start of the loop, the do...while loop checks its condition at the end of the loop.

A do...while loop iterates the elements for the infinite number of times like while loop. But, code is executed at least once whether condition is true or false.

Example

using System;

namespace do_while

{

    class Program

    {

        static void Main(string[] args)

        {

            int table, i, res;

            table = 12;

            i = 1;

            do

            {

               res = table * i;

               Console.WriteLine("{0} x {1} = {2}", table, i, res);

               i++;

            }

     // must put semi-colon(;) at the end of while condition in do...while loop.

            while (i <= 10);

            Console.ReadLine();

        }

    }

}

The for loop

The for loop iterates the elements for the fixed number of times. It should be used if number of iteration is known.

Example

using System;

namespace for_loop

{

    class Program

    {

        static void Main(string[] args)

        {

            int i;

            for (i = 1; i <= 10; i++)

            {

                Console.WriteLine("2 * "+i+" = "+2*i);

            }

            Console.ReadLine();

        }

    }

}


foreach loop

foreach loop is a different kind of looping constructs in C# programming that doesn’t includes initialization, termination and increment/decrement characteristics. It uses collection to take value one by one and then processes them.

Example

using System;

namespace foreach_loop

{

    class Program

    {

        static void Main(string[] args)

        {

            string[] name = new string[5]; // declaring array

            //Storing value in array element

            name[0] = "amit";

            name[1] = "anil";

            name[2] = "jay";

            name[3] = "anuj";

            name[4] = "akshay";

            //retrieving value using foreach loop

            foreach (string n in name)

            {

                Console.WriteLine("Hello " + n);

            }

            Console.ReadLine();

        }

    }

}