Visual Basic 2005 in a Nutshell, Third Edition

110

|

Chapter 7: The .NET Framework Class Library

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

General Multiplier

A set of curly braces with two comma-delimited integer values indicates a

repeated match a specific number of times. The format is

{x,y}, where x and

y are nonnegative integers, and matches if and only if there are at least x but

at most

y instances of the single character preceding the opening bracket. For

example, the regular expression

\da{5,10}\d matches any string beginning

with a single digit, continuing with at least 5 but at most 10

as and ending

with a single digit, as with

0aaaaaa1.

You can leave out one of

x or y. Thus, {x,} means “at least x,” and {,y}

means “at most y.”

Escaped Characters

Several characters have special meaning within regular expression patterns,

such as [ and ?. These characters must be escaped with the backslash char-

acter (

\) before they can be matched as ordinary non-special characters. For

instance,

\[ matches an opening bracket, \? matches a question mark, and \\

matches a backslash.

The System.Text.RegularExpressions namespace has a Regex class, which has

objects that represent regular expressions. Here’s a simple example of using the

Regex class.

Dim matchPattern As New System.Text.RegularExpressions.Regex( _

"\da{3,5}\d")

MsgBox(matchPattern.IsMatch("0a1")) ' Displays False

MsgBox(matchPattern.IsMatch("0aaa1")) ...