using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"(^[%@]\tfor\t)(.*[\w\s:]??)(?![→←].*)(\[sound.*)";
string substitution = @"\1\2\t\3";
string input = @"% for 1 <i><font color=""#ab0000"">British English</font></i> to make something seem less successful, interesting, good etc than it really is: [sound:_p008-000614203.mp3] the pessimists who are talking down Britain →贬低英国的悲观主义者
@ for to talk to someone as if they are stupid, although they are not ←以高人一等的口气对〔某人〕说话； <i><font color=""#efefef"" style=""background-color: rgb(141, 141, 141);"">SYN</font></i> patronize: [sound:_p008-000614218.mp3] The students felt that they were talked down to as though they were children. →这些学生感到和他们说话的都是一副居高临下的口气，好像他们是小孩一样。
@ for talk somebody into doing something [sound:_p008-000614234.mp3] My husband talked me into going skiing. →我的丈夫说服我去滑雪。
";
RegexOptions options = RegexOptions.Multiline;
Regex regex = new Regex(pattern, options);
string result = regex.Replace(input, substitution);
}
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx