VB.NET Control Statements

In VB.NET, the control statements are the statements that controls the execution of the program on the basis of the specified condition. It is useful for determining whether a condition is true or not. If the condition is true, a single or block of statement is executed. In the control statement, we will use if- Then, if Then Else, if Then ElseIf and the Select case statement.

We can define more than one condition to be evaluated by the program with statements. If the defined condition is true, the statement or block executes according to the condition, and if the condition is false, another statement is executed.

The following figure shows a common format of the decision control statements to validate and execute a statement:

The above diagram shows that if the defined condition is true, statement_1 will be executed, and if the condition is false, statement_2 will be executed.

VB.NET provides the following conditional or decision-making statements.

If-Then Statement
If-Then Else Statement
If-Then ElseIf Statement
Select Case Statement
Nested Select Case Statements

If-Then Statement

The If-Then Statement is a control statement that defines one or more conditions, and if the particular condition is satisfied, it executes a piece of information or statements.

Syntax:

In If-Then Statement, the condition can be a Boolean, logical, or relational condition, and the statement can be single or group of statements that will be executed when the condition is true.

Example 1: Write a simple program to print a statement in VB.NET.

Module1.vb

  Module Module1  ‘ Declaration of variable str      Dim str As String = “tutoraspire”      Sub Main()          ‘ if str equal to “tutoraspire”, below Statement will be executed.          If str = “tutoraspire” Then              Console.WriteLine(“Welcome to the tutoraspire”)          End If  Console.WritLine(“press any key to exit?”)  Console.ReadKey()      End Sub  End Module  

Now compile and execute the above program by clicking on the Start or F5 button, it shows the following output:

VB.NET Control Statements

As we can see in the above example, if the value of str is equal to tutoraspire, the condition is true, and it prints the Statement.

Example 2: Write a program to print a number is greater than another number in VB.NET.

if_statment2.vb

  Module if_statement2      Sub Main()          ?Definition of variables          Dim no1, no2 As Integer          Console.WriteLine(“Enter any two number:”)          no1 = Console.ReadLine() ?read no1 from user          no2 = Console.ReadLine() ?read no2 from user          If no1 > no2 Then              Console.WriteLine(“First number is greater than second number”)          End If          If no1 < no2 Then              Console.WriteLine(“Second number is greater than First number”)          End If          Console.WriteLine(“press any key to exit…”)          Console.ReadKey()   End Sub  End Module  

Now compile and execute the above program by clicking on the Start or F5 button, it shows the following output:

VB.NET Control Statements

In the above program, we enter two numbers to find the greater number using the relational operator. And if the first number is greater than the other, the first statement is executed; otherwise, the second statement will be executed.

If-Then-Else Statement

The If-Then Statement can execute single or multiple statements when the condition is true, but when the expression evaluates to false, it does nothing. So, here comes the If-Then-Else Statement. The IF-Then-Else Statement is telling what If condition to do when if the statement is false, it executes the Else statement. Following is the If-Then-Else statement syntax in VB.NET as follows:

Syntax:

  If (Boolean_expression) Then  ‘This statement will execute if the Boolean condition is true  Else  ‘Optional statement will execute if the Boolean condition is false  End If  

Flow chart

VB.NET Control Statements

The above diagram represents that if the Boolean expression (condition) is true, the if statement will execute, and if the Boolean expression is false, Else code or statement will be executed. After that, the control transfer to the next statement, which is immediately after the If-Then-Else control statement.

Example 1: Write a program to check whether the number is even or odd.

If_Else_statment.vb

  Module If_Else_statement      Sub Main()          Dim num As Integer          Console.WriteLine(“Enter the Number”)          num = Console.ReadLine() ‘read data from console            If (num Mod 2 = 0) Then ‘ if condition is true, print the if statement              Console.WriteLine(“It is an even number”)            Else ‘otherwise, Else statement is executed.              Console.WriteLine(“It is an odd number”)          End If    Console.WriteLine(“press any key to exit…”)          Console.ReadKey()      End Sub  End Module  

Now compile and execute the above program by clicking on the Start or F5 button, it shows the following output:

VB.NET Control Statements

Example 2: Write a program to print the larger and smaller of the two numbers.

if_else_statment2.vb

  Module if_else_statement2      Sub Main()          Dim a As Integer          Dim b As Integer          Console.WriteLine(“Enter the first number : “)          a = Console.ReadLine()            Console.WriteLine(“Enter the second number : “)          b = Console.ReadLine()            If a > b Then              Console.WriteLine(” larger number = {0} and smaller number = {1} “, a, b)          Else              Console.WriteLine(” larger number = {0} and smaller number = {1} “, b, a)          End If            Console.WriteLine(“press any key to exit…”)          Console.ReadKey()      End Sub  End Module  

Now compile and execute the above program by clicking on the Start or F5 button, it shows the following output:

VB.NET Control Statements

VB.NET If-Then-ElseIf statement

The If-Then-ElseIf Statement provides a choice to execute only one condition or statement from multiple statements. Execution starts from the top to bottom, and it checked for each If condition. And if the condition is met, the block of If the statement is executed. And if none of the conditions are true, the last block is executed. Following is the syntax of If-Then-ElseIf Statement in VB.NET as follows:

Syntax

  If(condition 1)Then     ‘ Executes when condition 1 is true   ElseIf( condition 2)Then     ‘ Executes when condition 2 is true   ElseIf( boolean_expression 3)Then     ‘ Executes when the condition 3 is true   Else      ‘ executes the default statement when none of the above conditions is true.   End If  

Flowchart

The following diagram represents the functioning of the If-Else-If Statement in the VB.NET programming language.

VB.NET Control Statements

If this condition is true in the flowchart of the if-else-if statement, the statement is executed within the if block. If the condition is not true, it passes control to the next ElseIf condition to check whether the condition is matched. And if none of the conditions are matched, the else block is executed.

Example 1: Write a program to show the uses of If… ElseIf statements.

if_elseIf.vb

  Module if_elseIf      Sub Main()          Dim var1 As Integer            Console.WriteLine(” Input the value of var1: “)          var1 = Console.ReadLine()          If var1 = 20 Then              ‘if condition is true then print the following statement’              Console.WriteLine(” Entered value is equal to 20″)          ElseIf var1 < 50 Then              Console.WriteLine(” Entered value is less than 50″)                     ElseIf var1 >= 100 Then              Console.WriteLine(” Entered value is greater than 100″)          Else              ‘if none of the above condition is satisfied, print the following statement              Console.WriteLine(” Value is not matched with above condition”)          End If          Console.WriteLine(” You have entered : {0}”, var1)          Console.WriteLine(” press any key to exit…”)          Console.ReadKey()      End Sub  End Module  

Now compile and execute the above program by clicking on the Start or F5 button, it shows the following output:

VB.NET Control Statements

Example 2: Write a program to use the If-Then-ElseIf Statement for calculating the division obtained by the student. Also, take the marks obtained by the student in 5 different subjects from the keyboard.

if_elseIf2.vb

  Module If_elseIf2        Sub Main()      ‘ execution start from Main() method          Dim m1, m2, m3, m4, m5, per As Integer          Console.WriteLine(“Enter marks in five subjects “)          ‘ Read the marks of five subject          m1 = Console.ReadLine()          m2 = Console.ReadLine()          m3 = Console.ReadLine()          m4 = Console.ReadLine()          m5 = Console.ReadLine()          per = (m1 + m2 + m3 + m4 + m5) / 5          If (per >= 70) Then              ‘if condition is true, print the first division              Console.WriteLine(” First division”)          ElseIf (per >= 60) Then              ‘if ElseIf condition is true, print the second division              Console.WriteLine(” Second division”)          ElseIf (per >= 50) Then              ‘if ElseIf condition is true, print the third division              Console.WriteLine(” Third division”)          ElseIf (per >= 40) Then              ‘if ElseIf condition is true, print only pass with grace               Console.WriteLine(” Only Pass with Grace”)          Else              ‘if none of the condition is true, print the Failed              Console.WriteLine(” Failed”)          End If          Console.WriteLine(“press any key to exit…”)          Console.ReadKey()      End Sub    End Module  

Now compile and execute the above program by clicking on the Start or F5 button, it shows the following output:

VB.NET Control Statements

Select Case Statement

In VB.NET, the Select Case statement is a collection of multiple case statements, which allows executing a single case statement from the list of statements. A selected case statement uses a variable to test for equality against multiple cases or statements in a program. If the variable is matched with any test cases, that statement will be executed. And if the condition is not matched with any cases, it executes the default statement.

Using the select case statement in VB.NET programming, you can replace the uses of multiple If-Then-Else If statement from the program for better readability and easy to use.

Syntax

Following is the syntax of the Select Case statement in VB.NET, as follows:

  Select Case [variable or expression]  Case value1 ‘defines the item or value that you want to match.  // Define a statement to execute    Case value2 ‘defines the item or value that you want to match.  // Define a statement to execute    Case Else  // Define the default statement if none of the conditions is true.  End Select   

Furthermore, you can also set more than one condition in a single case statement, such as:

  Select Case Variable / expression  Case value1  Statement1    Case value2, value3  Statement2    Case Else  // define the default statement if none of the condition is true  End Select   

Flowchart of Select Case Statement

The following flowchart represents the functioning of the Select case statement in the VB.NET programming language.

VB.NET Control Statements

In Flowchart, the Select Case statement represents the evaluating of the process start from top to bottom. If the expression or value is matched with the first select case, statement -1 is executed else the control transfer to the next case for checking whether the expression is matching or not. Similarly, it checks all Select case statements for evaluating. If none of the cases are matched, the Else block statement will be executed, and finally, the Select Case Statement will come to an end.

Example 1: Write a program to display the Days name using the select case statement in VB.NET.

Select_case.vb

  Imports System  Module Select_case      Sub Main()          ‘define a local variable.           Dim Days As String          Days = “Thurs”          Select Case Days              Case “Mon”                  Console.WriteLine(” Today is Monday”)              Case “Tue”                  Console.WriteLine(” Today is Tuesday”)              Case “Wed”                  Console.WriteLine(“Today is Wednesday”)              Case “Thurs”                  Console.WriteLine(“Today is Thursday”)              Case “Fri”                  Console.WriteLine(“Today is Friday”)              Case “Sat”                  Console.WriteLine(“Today is Saturday”)              Case “Sun”                  Console.WriteLine(“Today is Sunday”)              Case Else                  Console.WriteLine(” You have typed Something wrong”)            End Select          Console.WriteLine(“You have selected : {0}”, Days)          Console.WriteLine(“Press any key to exit…”)          Console.ReadLine()      End Sub  End Module  

Now compile and execute the above program by clicking on the Start or F5 button, it shows the following output:

VB.NET Control Statements

In the select case statement, the value of Days “Thurs” will compare all the available select cases‘ values in a program. If a value matched with any condition, it prints the particular statement, and if the value is not matched with any select case statement, it prints the default message.

Example 2: Write a program to perform an arithmetic operation using the Select case statement in VB.NET.

Operation.vb

  Imports System  Module Operation      Sub main()          ‘declaration of the variables          Dim num1, num2, sum As Integer          Dim def As Char          ‘initialization of num1 and num2 variable          num1 = 2          num2 = 6          Console.WriteLine(” Want to perform any operation?”)          Console.WriteLine(” A for Addition”)          Console.WriteLine(” S for Subtraction”)          Console.WriteLine(” M for Multiplication”)          Console.WriteLine(” D for Division”)          Console.WriteLine(” Please enter any input”)          def = Console.ReadLine()          Select Case def              Case “A”                  ‘perform Addition                  sum = num1 + num2                  Console.WriteLine(” Addition of two number is :{0}”, sum)              Case “S”                  ‘perform Subtraction                  sum = num2 – num1                  Console.WriteLine(” Subtraction of two number is :{0}”, sum)              Case “M”                  ‘perform Multiplication                  sum = num1 * num2                  Console.WriteLine(” Multiplication of two number is :{0}”, sum)              Case “D”                  ‘Peform Division                  sum = num2 / num1                  Console.WriteLine(” Division of two number is :{0}”, sum)              Case Else                  ‘If none of the operation matched, call default statement                  Console.WriteLine(” Please enter only define operation With Capital letter”)          End Select          Console.WriteLine(“Press any key to exit…”)          Console.ReadKey()      End Sub  End Module   

Now compile and execute the above program by clicking on the Start or F5 button, it shows the following output:

VB.NET Control Statements

In the above example, we defined Select with multiple case statements, and if the user-defined input is matched with any defined case statement, it executes that statement. And if the condition is not matched with any case, it executes a default statement in VB.NET.

Here, we provide ‘M’ as input, which checks all case statements, and if any case is matched with M, it executes the statement within the respective Case statement.

VB.NET Nested Select Case statements

When a Select Case statement is written inside the body of another Select Case statement is called a nested Select Case statement.

Syntax:

  Select Case “num”  ‘ code to be executed if num = 1  Case 1  ‘ nested Select case    Select Case n                                      ‘ code to be executed if n = 5                                    Case 5                                   Statement 1                                                                    ‘ code to be executed if n = 10                                   Case 10                                   Statement 2                                                                       ‘ code to be executed if n = 15                                    Case 15                                   Statement 3                                   ‘ code to be executed if n doesn’t match with any cases.                                 Case Else                                  Statement               ‘ code to be executed if num = 2              Case 2              Statement 2                           ‘ code to be executed if num = 3              Case 3             Statement 3                           ‘ code to be executed if num doesn’t match with any cases.              Case Else             Statement  

Example 1: Write a program to use a nested select case statement in VB.NET.

Module1.vb

  Module Module1        Sub Main()            Dim x As Integer = 10, y As Integer = 5          Select Case x                Case 10                  Console.WriteLine(“X Value: 10”)                      Select Case y                      Case 5                          Console.WriteLine(“Nested Switch Value: 5”)                               Select Case y – 2                              Case 3                                  Console.WriteLine(“Another Nested Switch Value: 3”)                            End Select                  End Select                 Case 15                  Console.WriteLine(“X Value: 15”)                Case 20                  Console.WriteLine(“X Value: 20”)                Case Else                  Console.WriteLine(“Not Known”)            End Select          Console.WriteLine(“Press Enter Key to Exit..”)          Console.ReadLine()      End Sub  End Module  

Now compile and execute the above program by clicking on the Start or F5 button, it shows the following output:

VB.NET Control Statements

Example 2: Write a program to use the nested select case statement in VB.NET.

nested_selectcase.vb

  Imports System  Module nested_selectcase      Sub Main()          Dim num As Integer          Dim str As String          str = “F”            Console.WriteLine(” Enter only First three number like 1, 2, 3″)          num = Console.ReadLine() ‘take input from the user          Select Case num              Case 1                  Console.WriteLine(” You are in block 1″)                  Console.WriteLine(“Only First two letter such as A and B”)                    str = Console.ReadLine()                  Select Case str                      Case “A”, “a”                          Console.WriteLine(” This is a VB.NET Tutorial”)                      Case “B”, “b”                          Console.WriteLine(” Welcome to the tutoraspire”)                      Case Else                          Console.WriteLine(” Something is wrong”)                  End Select                Case 2                  Console.WriteLine(” You are in block 2″)                  Console.WriteLine(“Only First two letter such as C and D”)                  str = Console.ReadLine()                  Select Case str                      Case “C”, “c”                          Console.WriteLine(” Welcome to the World!”)                      Case “D”, “d”                          Console.WriteLine(” Want to go in Heaven”)                      Case Else                          Console.WriteLine(” Something is wrong”)                  End Select                Case 3                  Console.WriteLine(” You are in block 3″)                  Console.WriteLine(“Only First two letter such as E and F”)                  str = Console.ReadLine()                  Select Case str                      Case “E”, “e”                          Console.WriteLine(” VB.NET is a programming language to develop web, window, and console-based application. “)                      Case “F”, “f”                          Console.WriteLine(” You have to basic knowledge of c and c++”)                      Case Else                          Console.WriteLine(” Something is wrong”)                  End Select              Case Else                  Console.WriteLine(” Something is wrong”)          End Select          Console.ReadLine()      End Sub  End Module  

Now compile and execute the above program by clicking on the Start or F5 button, it shows the following output:

VB.NET Control Statements

In the above example, we have only defined the first three numbers 1-3 and if the number matches to any case statement, the select statement is executed. Here, we have entered 2 that is matched with case 2 and it executes a block as shown above. And this block executes the statement “Only the First two letters such as C and D”. Therefore, we enter a letter D, letter D is matched with the nested select case statement, and if a match is found, it executes the select case statement as shown above.

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VB.NET Nested Select Case statements

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