#Regular expression not value how to#
#Regular expression not value full#

Here is a regex that will accept form input, as long as it doesn't contain any HTML or JSP comment tags: Source Listing Found a typo or mistake in the post? How irresponsible of me not to do that now.

#Regular expression not value how to#

In a later installment, IРІР‚в„ўll explain in more detail just what the code is doing and how to use the compiled assembly. Rather, you should consider adding it to a regular expression library assembly.Р”ВonРІР‚в„ўt know how? Well IРІР‚в„ўll show you a code listing for an exe that when run, builds a fully compiled version of this regular expression into an assembly that you can then reference in any project. However I wouldnРІР‚в„ўt recommend you just plunk that down in your code. ItРІР‚в„ўs a modified version of the one presented in FriedlРІР‚в„ўs book

#Regular expression not value full#

The full expression for matching an HTML tag is that lovely mash of characters presented at the very beginning of this post. However using the lazy evaluation consumes the fewest characters that match the expression, thus the first match using '.*?' would be 'test' and the second match is 'test2'.

The portion '.*?' uses lazy evaluation (the РІР‚Сљlazy starРІР‚Сњ) to match as few characters as possible. Another way to express this is to use lazy evaluation as such: The portion '*' matches a double quote, followed by any non double quote characters, followed by a double quote. In the first case, you could do the following: Name='double quoted value' name='single quoted value' name=notquotedvaluewithnowhitespace nameР”В®ach of these cases are quite simple. Now there are four possible formats for an Html attribute We have to consider the fact that the greater-than symbol does not end a tag if itРІР‚в„ўs within a quoted attribute value. Unfortunately, this implementation is too naive. Do you see it? What if I asked you to match the following tag? Now this will probably work 99 times out of 100, but thereРІР‚в„ўs a flaw in this expression. Roughly Translated, this expression looks for the beginning tag and tag name, followed by some white-space and then anything that doesnРІР‚в„ўt end the tag. You might consider the following expression: When you initially think to parse an HTML tag, it seems quite easy. So letРІР‚в„ўs look at a common task of matching HTML tags within the body of some text. Reading it will make your Regex-Fu powerful. This is really THE book on Regular Expressions. To that end, I recommend Mastering Regular Expressions by Jeffrey Friedl. They should be on the tool belt of every developer.

But after a few projects that required some intense text processing, I realized the power and utility of regular expressions.

All I needed was a Substring method and an IndexOf method and I was set. Ok I admit, I was a bit intimidated by regular expressions when I first started off as a developer.