C#正则表达式有意想不到的结果

Question

我有一个正则表达式,它应该匹配一个字符串中的"S".我使用了以下版本,它通过拒绝字符串"圣查尔斯"来工作:

regex = new Regex(@"(^|\s)(?<stuff>S?)(\s|$)");
Match match = regex.Match("Saint Charles");

比赛按预期失败.

我的问题是下面的第二个版本如何接受字符串:

regex = new Regex(@"(^|\b)(?<stuff>S?)(\b|$)");
Match match = regex.Match("Saint Charles");

比赛成功,但我预计它会失败.

更新: 以下是我的目标背景:

我有一个错误拼写或需要不同措辞的位置列表:

string[] locationNames =
            {
                "Ponte Vedra Beac",
                "Newton Upper Fal",
                "Howey In The Hil",
                "Mc Donough",
                "East Mc Dowell",
                "Saint Charles",
                "Cape Saint Clair",
                "Marine On Saint",
                "W Mifflin Fin",
                "Mt Sylvan",
                "Bromley Mtn",
                "S Richmond Hill"
            }; 

通过查看数据,我确定一些替换应发生在位置名称的末尾,一些替换发生在开头,而其他位于其中的任何位置.

我正在使用字典来确定1)正确的替换和2)所需的正则表达式的类型.

var alternateSpellings = new Dictionary<string, string>()
                                {
                                    {"Beac$", "Beach"},
                                    {"Fal$", "Falls"},
                                    {"Hil$", "Hills"},
                                    {"Mc ", "Mc"},
                                    {"\bMt\b", "Mount"},
                                    {"\bMtn\b", "Mountain"},
                                    {"\bS\b", "South"},
                                    {"\bSaint\b", "St."}

                                };

我循环遍历列表,并根据嵌入的元字符选择正则表达式.选项是:

regex = new Regex(".*(?<stuff>" + alternateSpelling.Key.Replace("$", "") + ")$");

要么

regex = new Regex(@"(^|\s)(?<stuff>" + alternateSpelling.Key.Replace("\b", "") + @")(\s|$)");

注意:我放弃了\b赞成\s OR

regex = new Regex(".*(?<stuff>" + alternateSpelling.Key + ").*");

一旦我找到匹配,我就做了替换......

if (match.Success)
                {
                    var stuff = match.Groups["stuff"].Value;
                    var stuffPosition = match.Groups["stuff"].Index;

                    newLocationName = locationName.Remove(stuffPosition, stuff.Length).Insert(stuffPosition, alternateSpelling.Value);

                }

Answer 1

怎么(^|\b)(?<stuff>S?)(\b|$) 匹配Saint Charles

^      =>   Start of String
             Saint Charles
            ^

S?     =>    which is optional. Tries to match

             Saint Charles
             ^

(\b|$) =>    Tries for \b or $ after S. But cannot match. Backtracks to start

             Saint Charles
            ^
\b     =>    Matches at the start of the string

             Saint Charles 
             ^

因此成功

• \b匹配单词边界.那是在字符串的开头和结尾

怎么纠正

S通过删除?帮助来匹配仅包含简单修改的单词

(^|\b)(?<stuff>S)(\b|$)

正则表达式示例