Types of Operators in Visual Basic (Page 1 of 4 )
In this second part of a two-part article, you will learn about comparison operators, the like operator, and more. It is excerpted from chapter five of the book
Visual Basic 2005 in a Nutshell, Third Edition, written by Tim Patrick, Steven Roman, Ph.D., Ron Petrusha and Paul Lomax (O'Reilly; ISBN: 059610152X). Copyright © 2006 O'Reilly Media, Inc. All rights reserved. Used with permission from the publisher. Available from booksellers or direct from O'Reilly Media.
Comparison Operators
There are three main comparison operators: < (less than), > (greater than), and = (equal to). They can be used individually, or any two operators can be combined with each other to form other comparison operators. The general syntax is:
result = expression1 <operator> expression2
The result is a Boolean value of True or False.
The following list indicates the condition required with each VB comparison operator to return a value of True.
= (Equal To)
True if expression1 is equal to expression2
< (Less Than)
True if expression1 is less than (and not equal to)
expression2
> (Greater Than)
True if expression1 is greater than (and not
equal to) expression2
<= (Less Than or Equal To)
True if expression1 is less than or equal to
expression2
>= (Greater Than or Equal To)
True if expression1 is greater than or equal to
expression2
<> (Not Equal To)
True if expression1 is not equal to expression2
Comparison operators can be used with both numeric and string expressions. If one expression is numeric and the other is a string, the string is first converted to a number of type Double (nonnumeric strings throw an exception). If both expression1 and expression2 are strings, the "greatest" string is the one that appears second in sort order. The sorting is based on the current character code page in use by the application, the region-specific locale information, and the OptionCompare setting. If that setting is Binary, the comparison is case-sensitive, whereas a setting of Text results in a case-insensitive comparison.
New in 2005. There are two "hidden" operators in Visual Basic: IsTrue(arg) and IsFalse(arg). They return a Boolean value that indicates whether the supplied argument is True or False, respectively. You cannot use them directly in your code, but they do exist, beginning in the 2005 release of Visual Basic, to support operator overloading. This is covered in the "Operator Overloading" section later in this chapter.
Next: The Like Operator >>
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 This article is excerpted from chapter five of the book Visual Basic 2005 in a Nutshell, Third Edition, written by Tim Patrick, Steven Roman, Ph.D., Ron Petrusha and Paul Lomax (O'Reilly; ISBN: 059610152X). Check it out today at your favorite bookstore. Buy this book now.
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