5.5. Comparison OperatorsThere 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.
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. 5.5.1. The Like OperatorThe Like operator is used to match a string against a pattern. It compares a string expression or literal with a string pattern expression and determines whether they match (the result is true) or not (the result is False). For example: If (testString Like "[A-Z]#") Then matches a capital letter followed by a digit. For details on the use of this operator, including special characters used in the pattern string, see the "Like Operator" entry in Chapter 12. |