c#正则表达式提取字符串--以SLA开头，$结束的信息

FO1140,45^BY3^BQN,2,6^FDMM,A1PLMBT3904LT1G$1TLA2147000A092$9D2148$Q30000000$SLA9121468FF40QA$A3360300880^FS^PQLEN000,0,1,Y

string pattern2 = @"SLA(?.*)\$";

            Match m2 = Regex.Match(s2,pattern2);
            if(m2.Success)
            {
                MessageBox.Show(m2.Groups["a"].Value);
            }