Conditional and Logical Operators in Visual Basic .NET

Tags: VB.NET, VB 2008, VB 2010, VB 2012, VB 2013

This lesson describes the Conditional and Logical operators.

For building complex expressions, VB.NET offers an expected set of Logical and Bitwise Operators as shown below:

Not Is performing logical negation on a Boolean expression, or bitwise negation on a numeric expression. (For a Boolean negation, the data type of the result is Boolean. For a bitwise negation, the result data type is the same as that of expression but if expression is Decimal, the result is Long.)

Dim IsUsernameValid As Boolean
IsUsernameValid = Not (Username.Text = "admin")                        


And Is performing a logical conjunction on two Boolean expressions, or a bitwise conjunction on two numeric expressions. (In a Boolean comparison, the And operator always evaluates both expressions)
Dim IsUserValid As Boolean
IsUserValid = (Username.Text = "admin") And (Password.Text = "mypwd")


AndAlso Is performing short-circuiting logical conjunction on two expressions (In a Boolean comparison, AndAlso performs short-circuiting, which means that if expression1 is False, then expression2 is not evaluated.)
Dim IsUserValid As Boolean
IsUserValid = (Username.Text = "admin") AndAlso (Password.Text = "mypwd")


Or Is performing a logical disjunction on two Boolean expressions, or a bitwise disjunction on two numeric expression (In a Boolean comparison, the Or operator always evaluates both expressions)
Dim IsPasswordValid As Boolean
IsPasswordValid = (Password.Text = "mypass") Or (Password.Text = "mypwd")


OrElse Is performing short-circuiting inclusive logical disjunction on two expressions (In a Boolean comparison, OrElse performs short-circuiting which means that if expression1 is True, then expression2 is not evaluated.)
Dim IsPasswordValid As Boolean
IsPasswordValid = (Password.Text = "mypwd") OrElse (Password.Text = "mypass")


Xor Is performing a logical exclusion on two Boolean expressions, or a bitwise exclusion on two numeric expressions. (In a Boolean comparison, the Xor operator always evaluates both expressions as there is no short-circuiting counterpart to Xor, because the result always depends on both operands.)
Dim IsUsernameValid As Boolean
IsUsernameValid = (Username.Text = "admin") Xor (Username.Text = "user")

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