C#中正则表达式的高级应用
1。在正则表达式中定义变量并调用：
using System; using System.Text.RegularExpressions;
publicclass Test {
publicstaticvoid Main () {
// Define a regular expression for repeated words. Regex rx =new Regex(@"\b(?<word>\w+)\s+(\k<word>)\b", RegexOptions.Compiled | RegexOptions.IgnoreCase);
// Define a test string. string text ="The the quick brown fox fox jumped over the lazy dog dog."; // Find matches. MatchCollection matches = rx.Matches(text);
// Report the number of matches found. Console.WriteLine("{0} matches found.", matches.Count);
// Report on each match. foreach (Match match in matches) { string word = match.Groups["word"].Value; int index = match.Index; Console.WriteLine("{0} repeated at position {1}", word, index); } } }
其中?<word>定义了一个变量，之后的\k<word>调用自身定义的变量word。publicclass Test {
publicstaticvoid Main () {
// Define a regular expression for repeated words. Regex rx =new Regex(@"\b(?<word>\w+)\s+(\k<word>)\b", RegexOptions.Compiled | RegexOptions.IgnoreCase);
// Define a test string. string text ="The the quick brown fox fox jumped over the lazy dog dog."; // Find matches. MatchCollection matches = rx.Matches(text);
// Report the number of matches found. Console.WriteLine("{0} matches found.", matches.Count);
// Report on each match. foreach (Match match in matches) { string word = match.Groups["word"].Value; int index = match.Index; Console.WriteLine("{0} repeated at position {1}", word, index); } } }
2。好用的Regex.Replace 和Match.Result
这个例子实现输入的日期更改格式的功能，用正则表达式自动搜索字符串并替换，注意正则表达式中变量的使用。
publicstring MDYToDMY(string input) { return Regex.Replace(input, "\\b(?<month>\\d{1,2})/(?<day>\\d{1,2})/(?<year>\\d{2,4})\\b", "${day}-${month}-${year}"); }
Match.Result是返回一个可以带正则表达式中变量值的字符串。
publicstring Extension(string url) { Regex r =new Regex(@"^(?<proto>\w+)://[^/]+?(?<port>:\d+)?/", RegexOptions.Compiled); return r.Match(url).Result("${proto}${port}"); }
正则式官方详解：
