VB.NET Language in a Nutshell, Second Edition

Logical and Bitwise Operators

Logical operators allow you to evaluate one or more expressions and return a Boolean value (True or False). VB.NET supports four logical operators: And, AndAlso, Or, OrElse, Not, and Xor. These operators also double as bitwise operators. A bitwise comparison examines the bit positions in both expressions and sets or clears the corresponding bit in the result, depending upon the operator used. The result of a bitwise operation is a numeric value.

In performing logical operations, VB.NET, unlike VB 6, uses conditional short- circuiting. This means that, in compound logical expressions, the individual expressions are evaluated only until the expression’s overall value is known, unless one of the individual expressions involves a call to another function or subroutine. Short-circuiting can occur in logical And operations when the first operand evaluates to False, as well as in logical Or operations when the first operand evaluates to True.

The six logical and bitwise operators are:

And

Performs logical conjunction; that is, it returns True if and only if both expression1 and expression2 evaluate to True. If either expression is False, then the result is False. If either expression is Null, then the result is Null. Its syntax is:

                        result = expression1 And expression2

For example:

If (x = 5) And (y < 7) Then

In this case, the code after the If statement will be executed only if the value of x is five and the value of y is less than seven.

As a bitwise operator, ...