ASP.Net c# 正则表达式 子表达式 group

public static string IgetNumber(string strQq)
{
    var result = string.Empty;
    const string pattern = @"[1-9][0-9]{4,}";
    var reg = new Regex(pattern, RegexOptions.IgnoreCase);
    var mc = reg.Matches(str);
   // if (mc.Count <= 0) return result;
    var rc = 0;
    foreach (Match m in mc)
    {
        if (rc == 0)
        {
            result = m.ToString();
            rc = 1;
        }
        else
        {
            result += "," + m;
        }
    }
    return result;
}