如何在字符串中查找特定句子的所有出现？

假设我有一个这样的字符串：

string source = "Today is friday! I'm am having trouble programming this. Today is friday! Tomorrow is saturday. Today is friday!" 

我想搜索这个字符串，抓住所有句子，说“今天是星期五！”，然后用我刚发现的句子创建一个新的字符串。

上述字符串的预期结果是：

 string output = "Today is friday!Today is friday!Today is friday!" 

编辑：LINQ不是强制性的。

谢谢！

Answer 1

这是一个非LINQ方法：

 string str = "Today is friday! I'm am having trouble programming this. Today is friday! Tomorrow is saturday. Today is friday!"; StringBuilder sb = new StringBuilder(); int index = 0; do { index = str.IndexOf("Today is friday!", index); if (index != -1) { sb.Append("Today is friday!"); index++; } } while (index != -1); string repeats = sb.ToString(); 

Answer 2

实际上没有必要找到比赛。 由于您是基于搜索模式创建新字符串，因此只需计算搜索字符串的出现次数就足够了。 如果您愿意，可以使用更快的子字符串计数算法替换正则表达式。

 string source = "Today is friday! I'm am having trouble programming this. Today is friday! Tomorrow is saturday. Today is friday!"; string searchPattern = "Today is friday!"; int count = Regex.Matches(source, searchPattern).Count; string result = string.Concat(Enumerable.Repeat(searchPattern, count)); 

Answer 3

正则表达式

找：

 .*?(Today is friday).*?(?=\1|$) 

更换：

 $1 

说明

 .*? # match everything before an occurrence of the sentence (Today is friday!) # match the sentence .*? # match everything after the sentence... (?=\1|$) # ...up to the next occurrence or end of the string 

Answer 4

好吧，你需要做的第一件事就是把你的一个字符串变成很多。 String.Split（）应该在这里工作，不需要正则表达式：

 var sentences = inputString.Split('.','!'); 

一旦你有了单独的句子，你只需要找到符合标准的句子：

 var todayIsFridaySentences = sentences.Where(s=>s.Contains("Today is friday")); 

……最后把它们放回原处; 如果你绝对必须使用Linq：

 var ouputString = todayIsFridaySentences .Aggregate(new StringBuilder(), (s,b) => b.Append(s)) .ToString();