Looping statements

Looping/Iterative Statements in Vb.NET

1. VB.NET:- Loop Statements BCA -501

2. 2 Content Introduction Looping Statement Advantages of Looping Statements Types of Looping Statements

3. 3 What is Looping Statement? A   Loop  is used to repeat the same process multiple times until it meets the specified condition in a program . By using a loop in a program, a programmer can repeat any number of statements up to the desired number of repetitions. A loop also provides the suitability to a programmer to repeat the statement in a program according to the requirement . A loop is also used to reduce the program  complexity, easy to understand , and easy to  debug .

4. 4 Advantages of Looping Statements It provides code iteration functionality in a program . It executes the statement until the specified condition is true . It helps in reducing the size of the code . It reduces compile time.

5. 5 Types of Loop Constructs VB.NET supports following types of loop: While..End While Do…..Loop For … Next For Each… Next

6. 6 While… End Loop Constructs The  While End loop  is used to execute blocks of code or statements in a program, as long as the given  condition  is true . It is useful when the number of executions of a block is not known. It is also known as an  entry-controlled loop  statement, which means it initially checks all loop conditions. If the condition is true, the body of the while loop is executed. This process of repeated execution of the body continues until the condition is not false. And if the condition is false, control is transferred out of the loop.

7. 7 While Loop-Syntax & Example Example: Imports  System   Module while_number Sub Main() 'declare x as an integer variable Dim x As Integer x = 1 ' Use While End condition While x <= 10 'If the condition is true, the statement will be executed. Console.WriteLine (" Number {0}", x) x = x + 1 ' Statement that change the value of the condition End While Console.WriteLine (" Press any key to exit...") Console.ReadKey () End Sub   End Module   Syntax: While [condition]       [ Statement to be executed ]   End While     

8. 8 Do-While Loop In VB.NET, Do While loop is used to execute blocks of statements in the program, as long as the condition remains true. It is similar to the While End Loop, but there is slight difference between them . The   while  loop  initially checks  the defined condition, if the condition becomes true, the while loop's statement is executed. Whereas in the  Do  loop, is opposite of the while loop, it means that it executes the Do statements, and then it checks the condition.

9. 9 Do-While Loop Example: Imports  System   Module  Do_loop        Sub Main()           '  Initializatio  and Declaration of variable  i            Dim  i  As Integer = 1           Do               ' Executes the following Statement                Console.WriteLine (" Value of variable I is : {0}",  i )                i  =  i  + 1 'Increment the variable  i  by 1           Loop While  i  <= 10 ' Define the While Condition               Console.WriteLine (" Press any key to exit...")            Console.ReadKey ()       End Sub   End Module   Syntax: Do    [ Statements to be executed]   Loop While  Boolean_expression    // or    Do    [Statement to be executed]   Loop Until  Boolean_expression   

10. 10 For…Next Loop A  For Next loop  is used to repeatedly execute a sequence of code or a block of code until a given condition is satisfied. A For loop is useful in such a case when we know how many times a block of code has to be executed. In VB.NET, the For loop is also known as For Next Loop.

11. 11 For Loop-Syntax For : It is the keyword that is present at the beginning of the definition. variable_name : It is a variable name, which is required in the For loop Statement. The value of the variable determines when to exit from the  For-Next loop,  and the value should only be a numeric. [Data Type] : It represents the Data Type of the  variable_name . start To end : The  start  and  end  are the two important parameters representing the initial and final values of the  variable_name . These parameters are helpful while the execution begins, the initial value of the variable is set by the start. Before the completion of each repetition, the variable's current value is compared with the end value. And if the value of the variable is less than the end value, the execution continues until the variable's current value is greater than the end value. And if the value is exceeded, the loop is terminated. Step : A step parameter is used to determine by which the  counter  value of a variable is increased or decreased after each iteration in a program. If the counter value is not specified; It uses 1 as the default value. Statements : A statement can be a single statement or group of statements that execute during the completion of each iteration in a loop. Next : In VB.NET a  Next  is a keyword that represents the end of the  For loop's Syntax: For  variable_name  As [  DataType  ] = start To end [ Step  step  ]   [ Statements to be executed ]   Next  

12. 12 For Loop- Example Imports System   Module Number       Sub Main()           ' It is a simple print statement, and ' vbCrLf ' is used to jump in the next line.            Console.Write (" The number starts from 1 to 10 " &  vbCrLf )           ' declare and initialize variable  i            For  i  As Integer = 1 To 10 Step 1               '  if  the condition is  true , the following statement will be executed                Console.WriteLine (" Number is {0} ",  i )               ' after completion of each iteration, next will update the variable counter           Next            Console.WriteLine (" Press any key to exit... ")            Console.ReadKey ()       End Sub   End Module  

13. 13 For…Each…Next Loop In the VB.NET,  For Each loop  is used to iterate block of statements in an array or collection objects. Using For Each loop, we can easily work with collection objects such as lists, arrays, etc., to execute each element of an array or in a collection. And when iteration through each element in the array or collection is complete, the control transferred to the next statement to end the loop . For Each loop  is used to read each element from the collection object or an array. The   Data Type  represents the type of the variable, and  var_name  is the name of the variable to access elements from the  array  or  collection object  so that it can be used in the body of For Each loop.

14. 14 For Each Loop-Syntax & Example Syntax: For Each  var_name  As [  DataType  ] In  Collection_Object    [ Statements to be executed]   Next   Imports System   Module  For_Each_loop        Sub Main()           'declare and initialize an array as integer           Dim  An_array () As Integer = { 1 ,  2 ,  3 ,  4 ,  5 }           Dim  i  As Integer 'Declare  i  as Integer              For Each  i  In  An_array                 Console.WriteLine ( " Value of  i  is {0}" ,  i )           Next            Console.WriteLine ( "Press any key to exit..." )            Console.ReadLine ()       End Sub   End Module