Shulou(Shulou.com)06/02 Report--

This article focuses on "what is the greedy feature of C# regular expression engine". Interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn "what is the greedy feature of C# regular expression engine?"

The greedy feature of the C # regular expression engine that matches as many characters as possible as long as the pattern allows. You can change the matching pattern to non-greedy by adding "?" after the "repeat description character" (*, +). Look at the following example:

Code string x = "Live for nothing,die for something"; Regex R1 = new Regex (@ ". * thing"); if (r1.IsMatch (x)) {Console.WriteLine ("match:" + r1.Match (x) .value); / / output: Live for nothing,die for something} Regex R2 = new Regex (@ ". *? thing"); if (r2.IsMatch (x)) {Console.WriteLine ("match:" + r2.Match (x) .Value) / / output: Live for nothing}

Use "(? >...)" Method to make a non-retroactive declaration. Due to the greedy nature of the C# regular expression engine, in some cases, it will backtrack to get a match, as shown in the following example:

Code string x = "Live for nothing,die for something"; Regex R1 = new Regex (@ ". * thing,"); if (r1.IsMatch (x)) {Console.WriteLine ("match:" + r1.Match (x) .value); / / output: Live for nothing,} Regex R2 = new Regex (@ "(? >. *) thing,"); if (r2.IsMatch (x)) / / mismatch {Console.WriteLine ("match:" + r2.Match (x) .Value) }

In R1, because of its greedy nature, ". *" will match all the way to the * of the string, and then match "thing", but fail at ",", where the engine will backtrack and match successfully at "thing,".

In R2, the entire expression match failed because non-backtracking was enforced.

At this point, I believe you have a deeper understanding of "what is the greedy feature of the C# regular expression engine?" you might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.