List<string> listcommand = new List<string>();

string sql = "update BMDMB set bmdmb_name=:bmdmb_name,parent_id=:parent_id where bmdmb_id=:bmdmb_id ";

            //string pattern = "(?is)(?<=" + Regex.Escape(":") + ").+?(?=" + Regex.Escape(",") + ")";

            //Regex reg = new Regex(@"(?<!@)[^\w$#@]@(?!@)[\w$#@]+");

            //reg.Match(yourStr).Value;//就是你要的 //@"(?<!@:)[^\w$#@:]:(?!@:)[\w$#@:]+"

            MatchCollection mats = Regex.Matches(sql, @"(?<p>:\w+)");//@"[^@@](?<p>@\w+)"

            foreach (Match mat in mats)

            {

                listcommand.Add(mat.Value);

            }

:bmdmb_name

:parent_id

:bmdmb_id