In Visual Basic .NET, the "If" statement is used for decision-making. "If" statement allows a program to execute different sets of statements depending on whether a certain condition is true or false.
The basic syntax of the "If" statement is:
If condition Then
'statements
End If
Where condition is an expression that evaluates to either true or false and statements are the code to be executed if the condition is true.
Here is an example:
Dim num As Integer = 5
If num > 0 Then
Console.WriteLine("Number is positive.")
End If
In this example, if num is greater than zero, the message "Number is positive" is printed to the console.
The "If" statement can be extended using the "Else" keyword to execute a different set of statements if the condition is false.
Here is an example:
Dim num As Integer = -5
If num > 0 Then
Console.WriteLine("Number is positive.")
Else
Console.WriteLine("Number is not positive.")
End If
In this example, since num is less than zero, the message "Number is not positive" is printed to the console.
The "If" statement can be further extended using the "ElseIf" keyword to test multiple conditions in a single statement.
Here is an example:
Dim num As Integer = 0
If num > 0 Then
Console.WriteLine("Number is positive.")
ElseIf num < 0 Then
Console.WriteLine("Number is negative.")
Else
Console.WriteLine("Number is zero.")
End If
In this example, since num is zero, the message "Number is zero" is printed to the console.
Finally, the "If" statement can be used with the assignment operator to assign a value to a variable based on a condition.
Here is an example:
Dim num As Integer = 0
num = If(num > 0, 1, -1)
Console.WriteLine("The value of num is " & num)
In this example, num is assigned the value of 1 if it is greater than zero, otherwise it is assigned the value of -1. The message "The value of num is 0" is printed to the console because num is initially 0.