"已经是一个开放的DataReader"异常,在ASP.NET中嵌套了SqlDataReader

Question

我想在下面的代码中使用嵌套的SqlDataReader,但我无法实现它.我得到"System.InvalidOperationException:已经有一个与此命令关联的打开的DataReader,必须先用代码关闭".有什么建议

            c = "select user_Reps.rep_key,Officers.Officer_Name from user_Reps left join Officers on user_Reps.rep_key = Officers.Officer_code where [user_key]="+userCode;
            if (c == null)
                c = sr.ReadToEnd();
            try
            {

                SqlCommand cmd = new SqlCommand(c, cn);
                cn.Open();
                SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                List<Dictionary<string, object>> list = new List<Dictionary<string, object>>();
                SqlDataReader rdr2;
                while (rdr.Read())
                {
                    string c2 = "select Active_Clients.Clients_code,Active_Clients.Clients_Name,Active_Clients.Geo_code  from Active_Clients where Active_Clients.[Officer_code] =" + rdr.GetValue(0) + " order by Clients_Name";
                    SqlCommand cmd2 = new SqlCommand(c2, cn);

                    rdr2 = cmd2.ExecuteReader(CommandBehavior.CloseConnection);


                    Dictionary<string, object> d = new Dictionary<string, object>(rdr.FieldCount+rdr2.FieldCount);
                    while (rdr2.Read())
                    {
                        int i = 0;
                        for (; i < rdr.FieldCount; i++)
                        {
                            d[rdr.GetName(i)] = rdr.GetValue(i);
                        }

                        for (; i < rdr2.FieldCount; i++)
                        {
                            d[rdr2.GetName(i)] = rdr2.GetValue(i);
                        }

                        list.Add(d);
                    }




                    rdr2.Close();

                    //list.Add(d);
                }
                JavaScriptSerializer j = new JavaScriptSerializer();
                Response.Write(j.Serialize(list.ToArray()));

            }

Answer 1

错误消息有点误导.除非您有MultipleActiveResultSets=True连接字符串,否则每个连接只能有一个活动结果集.如果每个读者都拥有它独立的SqlCommand对象,情况仍然如此.

Answer 2

您不能在同一连接上同时拥有两个打开的DataReader.

此问题的常见解决方案是在打开下一个DataReader之前将第一个DataReader的内容加载到DataTable或List <>中.您还可以为嵌套查询打开新连接.

编辑或,如@Mithrandir所述,您可以在连接字符串上使用MultipleActiveResultSets = true.