regular expressions

Question

Sir:

   What is the regular expressions? Why we use?(windows application not web)

  Can U Explain Regular expressions in C# windiws application?

  

 

Answer 1

 

Google, Exam question

 

etc.

 

However to me in my words

 

Regular Expressions are, of course, expressions. They define a string to search for in a larger string. You can then perform actions on the string/s you find.

 

Hard to explain .

 

 

But say we have a string. "abcdefg". You can define a regex to look for all "a" and all "e" and either remove all else or remove these entries. regex can get very complicated with expression that identify american phone numbers, can validate input and check it is a valid email or cc number.

 

You would use them on a Windows app to validate user input or perform complex string replace functions.

Answer 2

 

First read for example http://en.wikipedia.org/wiki/Regular_expression .

 

In C#-programs, regular expressions are frequently used to validate input data, for example to ensure that a zip code entered by a user actually looks like a zip code, that an e-mail entered looks like an e-mail adress etc.

 

They are also used to find and extract specific patterns from data,.

 

Often they are over-used. Regular expressions can easily become overly complex, and tend to be write-only/write-once code, very, very hard to maintain.

 

Before resorting regular expressions, you should think carefully if this is the right choice.

 

If you do decide to use regular expressions, check out RegexDesigner.NET at http://www.sellsbrothers.com/tools/#regexd, an invaluable tool to write and test regular expressions.

Answer 3

Check out this forum's top announcement post .Net Regex Resource Reference which has referential information geared towards all levels, expert to beginner, where you can find links to tools to use and how-to code examples.