Conditional Statements in VB.NET

Conditional Statements

If....Else statement

If conditional expression is one of the most useful control structures which allows us to execute a expression if a condition is true and execute a different expression if it is False. The syntax looks like this:

If condition Then
[statements]
Else If condition Then
[statements]
-
-
Else
[statements]
End If

Understanding the Syntax

If the condition is true, the statements following the Then keyword will be executed, else, the statements following the ElseIf will be checked and if true, will be executed, else, the statements in the else part will be executed.

Example

Imports System.Console
Module Module1

Sub Main()
Dim i As Integer
WriteLine("Enter an integer, 1 or 2 or 3")
i = Val(ReadLine())
'ReadLine() method is used to read from console

If i = 1 Then
WriteLine("One")
ElseIf i = 2 Then
WriteLine("Two")
ElseIf i = 3 Then
WriteLine("Three")
Else
WriteLine("Number not 1,2,3")
End If

End Sub

End Module

The image below displays output from above code.



Select....Case Statement

The Select Case statement executes one of several groups of statements depending on the value of an expression. If your code has the capability to handle different values of a particular variable then you can use a Select Case statement. You use Select Case to test an expression, determine which of the given cases it matches and execute the code in that matched case.

The syntax of the Select Case statement looks like this:

Select Case testexpression
[Case expressionlist-n
[statements-n]] . . .
[Case Else elsestatements]
End Select

Example

Imports System.Console
Module Module1

Sub Main()
Dim keyIn As Integer
WriteLine("Enter a number between 1 and 4")
keyIn = Val(ReadLine())

Select Case keyIn
Case 1
WriteLine("You entered 1")
Case 2
WriteLine("You entered 2")
Case 3
WriteLine("You entered 3")
Case 4
WriteLine("You entered 4")
End Select

End Sub

End Module

The image below displays output from above code.