public static int ExecuteNonQuery(string cmdText,
            params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connstr))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                     = cmdText;
                    cmd.Parameters.AddRange(parameters);
                    return cmd.ExecuteNonQuery();
         
                }
            }
        }

 我想问 这个方法里面using是什么意思  为什么用using   不用using不是更简单易懂么？ using有啥特殊含义？在线等