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:

If condition Then
[Statement or block of Statement]
End If

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 = "JavaTpoint"
    Sub Main()
        ' if str equal to "JavaTpoint", below Statement will be executed.
        If str = "JavaTpoint" Then
            Console.WriteLine("Welcome to the JavaTpoint")
        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:

As we can see in the above example, if the value of str is equal to JavaTpoint, 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:

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

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:

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 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.

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:

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:

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.

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:

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:

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:

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 JavaTpoint")
                    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:

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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