Regex r = new Regex("[\\*\\.\\?\\+\\$\\^\\[\\]\\(\\)\\{\\}\\|\\/]");
MatchCollection ms = r.Matches(input);
List<string> list = new List<string>();
foreach (Match item in ms)
{
if (list.Contains(item.Value))
continue;
input = input.Replace(item.Value, "\\" + item.Value);
list.Add(item.Value);
}
return input;
}