1. CIS 451: Regular Expressions Dr. Ralph D. Westfall January, 2009

2. Regular Expressions find patterns in text strings based on the idea of wild cards.e.g., dir s*.doc in DOS/Windows finds any.doc file starting with s, followed by any other character(s) find much more complicated patterns e.g., any one of a specified list of characters rather than just one or any e.g., any character except ones in a list

3. RegEx Class implements the concept of regular expressions in.NET languages could be used for E-commerce for input validation checking user inputs such as e-mail addresses, credit card #s, telephone #s, etc. to see if they match the typical patterns

4. Regular Expression Object create a regular expression object Dim reg as Regex reg = New Regex("[pattern]") could also create Regex object without a pattern, and then provide the pattern as an argument in a Regex method

5. .NET RegEx Patterns. ba. finds bat, bal, bac (matches any single character) ? bottles? finds bottle and bottles (0 or 1 of the character before ?) [3-9] finds 3, 4, … 9 (any 1 character in specified range) + to+ finds to, too (1 or more of before +) {#} b{2} finds any bb (# of preceding matches together)

6. .NET RegEx Patterns - 2 | or operator e.g., a|b finds a or b \ escape character to identify literals e.g., \. can combine different parameters [a-z]{3} finds any 3 letter word [0-9]{4}( |-)? finds any 4 #s, followed by 0 or 1 occurrence of space or dash (could use in credit card validation)

7. Regular Expression Object - 2 methods reg.IsMatch([string to search]) returns True if pattern is found in string reg.Match([string to search]) returns the matching characters in a string each time pattern is found reg.Replace([string1, string2]) replaces every occurrence of string1 with string2 'notes (here =.aspx)

8. Using Regular Expressions Dim ok as Boolean Dim reg As New Regex("[0-9]{4}( |-)?" & _ "[0-9]{4}( |-)?[0-9]{4}( |-)?[0-9]{4}", _ RegexOptions.Compiled) ok = reg.IsMatch("1234-4323-9876-6543") If ok Then Response.Write "String is OK" End If 'notes (here =.html)

9. Warning a regular expression may say a String is OK even if there are other characters around it e.g., Dim input as String Dim ok as Boolean input = "XYZ1234-4323-9876-6543XYZ" ok = reg.IsMatch(input) 'credit card If ok Then 'pattern MsgBox(input & " is OK") End If

10. Extracting Matches from Strings can use.Match() function to separate matching part from other characters around it e.g., Dim input as String input = "XYZ1234-4323-9876-6543XYZ" If reg.IsMatch(input) Then MsgBox(reg.Match(input) & " is OK") End If

11. More Regular Expressions Info Using Regular Expressions with.NET Regular Expressions Reference Google search (5+ million occurrences) Google search history of regular expressions concepts date back to 1940s (before computers) T-shirt

12. RegEx Exercises 1 explain the following e-mail address pattern [a-z]+@[a-z]+\.com 2 extend it to handle following endings: com, edu, org, net, gov, mil, int (must appear at least once) 3 modify it to allow numbers, dashes [-] and periods [.] after the 1st character

13. RegEx Exercises - 2 create patterns to validate zip codes both as 5-digit and Zip + 4 e.g., 90702 or 90702-7934 phone #s (intnl, long distance, and local) credit card numbers names (including middle initial, von, de, etc.) course #s (CIS, EBZ, CS; 1xx-4xx, etc.)

14. RegEx Exercises - 3 test text or files samples against regular expressions at Regular Expression Library's tester page and report backtester test regular expressions from previous pages in this PowerPoint others that you make up from Regular Expression LibraryRegular Expression Library

15. RegEx Exercises - 4 use Regular Expression Library's tester page to Load a Data Source from a URL and find data in the web page using a regular expression that you specifytester OR find free (trial) software that will do the same thing