使用RegEx类从电子邮件主题中删除“ RE：”（类似）

Question

I need to remove the leading RE: from a subject and it's definitely not my day today, because I don't get the match and obviously am missing something simple. My predecessor made it abundantly clear that the Substring approach works but I just can't stand bad technique. :)

//emailSubject = emailSubject.Substring(4);
emailSubject = Regex.Replace(emailSubject, @"^.{0, 3}:\s", "");

The way I see it, we should find the beginning of the string and get between zero and three characters followed by a colon and a space. Then, this junk should be removed.

The computer disagrees, though, and I'm out of ideas. What simple thing do I miss here?!

Answer 1

删除逗号后的空格：

@"^.{0,3}:\s"

Answer 2

You can remove all sort of stuffs such as re and fwd with the following regex:

^(?>(?:re|fwd) *: *)*

The regex above is to be used with RegexOptions.IgnoreCase .

It can even take care of multiple reply and forward, such as:

re: re : RE: fwd  : re: fwd:  About meeting tomorrow

Answer 3

If you are concerned about multiple FWD chains (and alikes) and multiple client languages:

    public static string ClearSubject(string originalSubject)
    {
        Regex regex = new Regex(@"^([\[\(] *)?(RE?S?|FYI|RIF|I|FS|VB|RV|ENC|ODP|PD|YNT|ILT|SV|VS|VL|AW|WG|ΑΠ|ΣΧΕΤ|ΠΡΘ|תגובה|הועבר|主题|转发|FWD?) *([-:;)\]][ :;\])-]*|$)|\]+ *$", RegexOptions.IgnoreCase);
        originalSubject = regex.Replace(originalSubject, string.Empty);

        if (regex.IsMatch(originalSubject))
        {
            return ClearSubject(originalSubject);
        }

        return originalSubject;
    }