Every now and then I need the ASP.NET RegularExpressionValidator control to validate some user input on a web-page using .NET Regular Expressions (which are very similar to regular expressions used in other languages and frameworks).

Somehow, I have lost loads of time because many of the hits on Google show up high in the results, but do not actually help that much.

So I decided to put up a bunch of links to pages that I think are relevant, or helped me much.
This list is not definitive: please comment when you have links to better information!

Note: this list is current at the instant of the latest edit timestamp: tools might have improved (or disappeared) since then.
Opnions are mine; if you do not agree: please convince me why.

Tools

Regular Expression builder applications

• Expresso – free .NET WinForms application to visually build and test regular expressions (free registraion required after 60 days of trial usage)
• RegexWorkbench – free .NET WinForms application to build and test regular expressions (much more rudimentary than Expresso)

Regular Expression test applications

• RegexLib tester – free on-line regular expresion tester where you can choose the client platform (.NET/ClientSide/SilverLight)
• The Regulator – free .NET WinForms application to test regular expressions with built in support for RegexLib.com
• The Regex Coach – free LISP Windows application to test regular expressions and tries to explain them in plain english
• RegExPal – free on-line JavaScript regular expression tester (tests the client side only)
• ReWork – free on-line JavaScript tester with samples in JavaScript/PHP/Python/Ruby
• RegexDesigner.NET – free .NET WinForms application to test regular expressions and generate C#/VB.NET code from them (ot really a “Designer” after all and much less sophisticated than The Regulator)

Tools lists

• SharpToolbox – list of Regular Expression tools
• RegexLib – list of regex resources, including tools

Tools not worth looking at

• Regulazy – too rudimentary

Sites/Documentation/Examples

• The well respected RegexLib.comsite:
  • CheatSheet of how regular expressions can be built
  • Search for regular expressions
  • Browse regular expressions
• MSDN documentation on JScript Regular Expressions – I wish this was more readable, but it is the definitive source on Microsoft’s JScript Regular Expression implementation
  MSDN documentation on the .NET Framework Regular Expressions, including
  Regular Expression Language – Quick Reference.
  Grouping Constructs in Regular Expressions.
  Anchors in Regular Expressions.
• The 30 Minute Regex Tutorial – CodeProject.
• C# Regular Expressions Cheat Sheet.
• RegEx questions on Stackoverflow.com
• Nice tutorial on regular expressions
• Stackoverflow thread on writing maintanable regular expressions (if that is at all possible <g>), with many good tips
• Stackoverflow thread on why regular expressions usually look so cryptic (which make them hard to read and write), including some tips on making them more readable
• JavaScript: Unicode Plugin for XRegExp

Some comments on common regular expression solutions

• RegEx for email usuaully reject valid email adresses like jeroen+info@pluimers.subdomain.info
  Dominic has some very nice info on validating email adresses
• RegEx for a minimum number of characters usually contain \w, which is not any character!
  Better use ^(.{6,})$ than ^(\w{6,})$ if you want a minimum length of 6 characters.

Bugs

• JScript/VBScript bug that is also present in Internet Explorer (almost any version): A JScript/VBScript Regex Lookahead Bug