sqldatareader 取值问题
String sn = "SELECT TOP (1) SN FROM ES_News ORDER BY SN DESC ";
  SqlCommand sqlcmd = new SqlCommand(sn, conn);
  SqlDataReader ss = cmd.ExecuteReader();
  if (ss.Read())
  {
  String a =ss["SN"].ToString();
  Response.Write(a);
  }
为什么不输出a的值？ 是取值有问题么 本人初学，麻烦给解释下..

------解决方案--------------------
SqlDataReader ss = sqlcmd.ExecuteReader();