Question

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！”，并用我刚刚找到的句子创建一个新字符串。

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

这是一种非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。由于您是根据搜索模式创建新字符串，因此只需搜索字符串的计数就足够了。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

查找

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

替换：

$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

好的，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，你只需要寻找符合标准的句子：

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

......然后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();

如何在字符串中查找特定句子的所有出现？

4 个答案:

正则表达式

说明