如何存储从 SqlDataReader 返回的结果？答案

【问题标题】：How to store results returned from SqlDataReader?如何存储从 SqlDataReader 返回的结果？
【发布时间】：2023-03-31 07:00:01
【问题描述】：

我是一个菜鸟，正如我的问题所证明的那样，我正在使用数据读取器来查找与某个 subId 值关联的行。我使用了一个 while(dr.read) 循环，并在每种情况下都将一个 switch case 语句与其他读取器嵌套（下面的代码），但我抛出了异常“已经是与此命令关联的开放数据读取器，必须首先关闭”。有没有办法将第一个数据读取器的结果（subId = x 的相关行）存储在数组或列表中，然后在我输入 switch 语句之前关闭该读取器？（我理解数组是什么，我认为它会起作用，但我不知道语法是什么样的）。

string viewQuery = "SELECT ProductId FROM SubmissionProducts WHERE SubmissionId =" + x;



            using (SqlCommand viewcmd = new SqlCommand(viewQuery, editConn))
            {
                SqlDataReader dr = viewcmd.ExecuteReader();
                while (dr.Read())
                {
                    switch(dr.GetInt32(0))
                    {
                        case 1:
                            PanelEplShow.Visible = true;
                            using (SqlCommand eplviewcmd = new SqlCommand(epl, editConn))
                            {
                                SqlDataReader epldr = eplviewcmd.ExecuteReader();
                                epldr.Read();
                                LblEplShowEntity.Text = epldr.GetString(0);
                                LblEplShowTotalEmpl.Text = epldr.GetInt32(1).ToString();
                                LblEplShowCalEmpl.Text = epldr.GetInt32(2).ToString();
                                LblEplShowMichEmpl.Text = epldr.GetInt32(3).ToString();
                                LblEplShowNyEmpl.Text = epldr.GetInt32(4).ToString();
                                LblEplShowNjEmpl.Text = epldr.GetInt32(5).ToString();
                                LblEplShowPrimEx.Text = epldr.GetInt32(6).ToString();
                                LblEplShowLim.Text = epldr.GetInt32(7).ToString();
                                LblEplShowPrem.Text = epldr.GetInt32(8).ToString();
                                LblEplShowWage.Text = epldr.GetInt32(9).ToString();
                                LblEplShowInvestCost.Text = epldr.GetInt32(10).ToString();
                                epldr.Close();
                            }
                            break;
                        case 2:
                            PanelProfShow.Visible = true;
                            using (SqlCommand profcmd1 = new SqlCommand(prof, editConn))
                            {
                                SqlDataReader profdr = profcmd1.ExecuteReader();
                                profdr.Read();
                                LblProfShowPrimEx.Text = profdr.GetInt32(0).ToString();
                                LblProfShowType.Text = profdr.GetInt32(1).ToString();
                                LblProfShowLim.Text = profdr.GetInt32(2).ToString();
                                LblProfShowRetention.Text = profdr.GetInt32(3).ToString();
                                LblProfShowAtt.Text = profdr.GetInt32(4).ToString();
                                LblProfShowPrem.Text = profdr.GetInt32(5).ToString();
                                LblProfShowSublim.Text = profdr.GetInt32(5).ToString();
                                LblProfShowEntity.Text = profdr.GetInt32(6).ToString();
                                profdr.Close();
                            }
                            break;
                        case 3:
                            PanelCrimeShow.Visible = true;
                            using (SqlCommand crimcmd = new SqlCommand(crim, editConn))
                            {
                                SqlDataReader crimdr = crimcmd.ExecuteReader();
                                crimdr.Read();
                                LblCrimeShowEntity.Text = crimdr.GetString(0);
                                LblCrimeShowEmpl.Text = crimdr.GetInt32(1).ToString();
                                LblCrimeShowPrimEx.Text = crimdr.GetInt32(2).ToString();
                                LblCrimeShowLimA.Text = crimdr.GetInt32(3).ToString();
                                LblCrimeShowDedA.Text = crimdr.GetInt32(4).ToString();
                                LblCrimeShowPremA.Text = crimdr.GetInt32(5).ToString();
                                LblCrimeShowLimB.Text = crimdr.GetInt32(6).ToString();
                                LblCrimeShowDedB.Text = crimdr.GetInt32(7).ToString();
                                LblCrimeShowPremB.Text = crimdr.GetInt32(8).ToString();
                                crimdr.Close();
                            }
                            break;
                        case 4:
                            PanelFidShow.Visible = true;
                            using (SqlCommand fidcmd = new SqlCommand(fid, editConn))
                            {
                                SqlDataReader fiddr = fidcmd.ExecuteReader();
                                fiddr.Read();
                                LblFidShowEntity.Text = fiddr.GetString(0);
                                LblFidShowPrimEx.Text = fiddr.GetInt32(1).ToString();
                                LblFidShowLim.Text = fiddr.GetInt32(2).ToString();
                                LblFidShowSir.Text = fiddr.GetInt32(3).ToString();
                                LblFidShowAtt.Text = fiddr.GetInt32(4).ToString();
                                LblFidShowPrem.Text = fiddr.GetInt32(5).ToString();
                                LblFidShowSublim.Text = fiddr.GetInt32(6).ToString();
                                fiddr.Close();
                            }
                            break;
                        case 5:
                            PanelNotShow.Visible = true;
                            using (SqlCommand notcmd = new SqlCommand(not, editConn))
                            {
                                SqlDataReader notdr = notcmd.ExecuteReader();
                                notdr.Read();
                                LblNotShowPrimEx.Text = notdr.GetInt32(0).ToString();
                                LblNotShowCov.Text = notdr.GetInt32(1).ToString();
                                LblNotShowSharedLim.Text = notdr.GetInt32(2).ToString();
                                LblNotShowTradLim.Text = notdr.GetInt32(3).ToString();
                                LblNotShowTradSir.Text = notdr.GetInt32(4).ToString();
                                LblNotShowEplLim.Text = notdr.GetInt32(5).ToString();
                                LblNotShowEplSir.Text = notdr.GetInt32(6).ToString();
                                LblNotShowEplPrem.Text = notdr.GetInt32(7).ToString();
                                LblNotShowSublim.Text = notdr.GetInt32(8).ToString();
                                notdr.Close();
                            }
                            break;
                        case 6:
                            PanelPrivShow.Visible = true;
                            using (SqlCommand privcmd = new SqlCommand(priv, editConn))
                            {
                                SqlDataReader privdr = privcmd.ExecuteReader();
                                privdr.Read();
                                LblPrivShowPrimEx.Text = privdr.GetInt32(0).ToString();
                                LblPrivShowSharedLim.Text = privdr.GetInt32(1).ToString();
                                LblPrivShowTradLim.Text = privdr.GetInt32(2).ToString();
                                LblPrivShowTradAtt.Text = privdr.GetInt32(3).ToString();
                                LblPrivShowTradSir.Text = privdr.GetInt32(4).ToString();
                                LblPrivShowTradPrem.Text = privdr.GetInt32(5).ToString();
                                LblPrivShowEplLim.Text = privdr.GetInt32(6).ToString();
                                LblPrivShowEplSir.Text = privdr.GetInt32(7).ToString();
                                LblPrivShowEplAtt.Text = privdr.GetInt32(8).ToString();
                                LblPrivShowEplPrem.Text = privdr.GetInt32(9).ToString();
                                LblPrivShowEplWage.Text = privdr.GetInt32(10).ToString();
                                LblPrivShowEplSublim.Text = privdr.GetInt32(11).ToString();
                                LblPrivShowFidLim.Text = privdr.GetInt32(12).ToString();
                                LblPrivShowFidSir.Text = privdr.GetInt32(13).ToString();
                                LblPrivShowFidAtt.Text = privdr.GetInt32(14).ToString();
                                LblPrivShowFidPrem.Text = privdr.GetInt32(15).ToString();
                                LblPrivShowFidSublim.Text = privdr.GetInt32(16).ToString();
                                privdr.Close();
                            }
                            break;
                        case 7:
                            PanelPubShow.Visible = true;
                            using (SqlCommand pubcmd = new SqlCommand(pub, editConn))
                            {
                                SqlDataReader pubdr = pubcmd.ExecuteReader();
                                pubdr.Read();
                                LblPubShowMark.Text = pubdr.GetInt32(0).ToString();
                                LblPubShowTick.Text = pubdr.GetInt32(1).ToString();
                                LblPubShowTrad.Text = pubdr.GetInt32(2).ToString();
                                LblPubShowDic.Text = pubdr.GetInt32(3).ToString();
                                LblPubShowLim.Text = pubdr.GetInt32(4).ToString();
                                LblPubShowSecSir.Text = pubdr.GetInt32(5).ToString();
                                LblPubShowAllSir.Text = pubdr.GetInt32(6).ToString();
                                LblPubShowPrem.Text = pubdr.GetInt32(7).ToString();
                                LblPubShowPrimEx.Text = pubdr.GetInt32(8).ToString();
                                LblPubShowAtt.Text = pubdr.GetInt32(9).ToString();
                                LblPubShowSublim.Text = pubdr.GetInt32(10).ToString();
                                pubdr.Close();
                            }
                            break;
                        default:
                            break;
                    }
                }
                dr.Close();`

【问题讨论】：

标签： c# asp.net sql-server visual-studio

【解决方案1】：

将其加载到DataTable。

SqlDataReader pubdr = pubcmd.ExecuteReader();
DataTable dt = new DataTable();
dt.Load(pubdr);

扩展 cmets：

foreach (DataRow dr in dt.Rows)
{
    LblEplShowEntity.Text = dr["FIELDNAME"].ToString();
    //...
}

【讨论】：

dt.Rows[rowindex][columnName/columnIndex]

【解决方案2】：

加载一个DataTable，无论如何它在内部都是一个持久化的DataReader

对于您消费、使用、丢弃的 DataReader。这就是 DataReader 的本质。如果您希望数据保留，您将使用 DataTable。简单，但经验法则很好。

【讨论】：

【解决方案3】：

假设 SubmissionId 在表 SubmissionProducts 中是唯一的，则您无需使用数据读取器进行查询。您可以改用命令对象的ExecuteScalar 方法。

如果您想从 DataReader 获取当前行中所有列值的数组，您可以使用 GetValues 方法，如下所示：

    SqlDataReader reader; // assumming the data reader is already opened 
    object[] columns = new object[reader.FieldCount];
    reader.GetValues(columns);// columns now contains all the values from the curent row

【讨论】：

很遗憾，不，SubmissionId 可以关联多个实例。

【解决方案4】：

我发现我必须调整连接字符串中的某些内容。我不知道这是否是 .Net 故障，或者是否只是使用嵌套阅读器时的必要调整，但我必须将 MultipleActiveResultSets="true" 添加到我存储的连接字符串中。之后，一切正常，不需要数据表。非常感谢所有回答的人。虽然我确信上面的答案也可能有效，但如果这个问题对将来的某个人有用，我会发布完整的代码来展示什么对我有用。请注意：如果您是编码新手，需要这篇文章，请将您的查询参数化。这个网站是一个培训项目，我被指示避免参数化，以便首先学习其他东西，但这是最重要的。鲍比桌ftw。

这是代码。

using System;
using System.Text;
using System.Collections.Generic;
using System.Linq;
using System.Data;
using System.Data.Sql;
using System.Data.SqlClient;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class View : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

        string x = Request.QueryString["SubmissionId"];
        string connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString;
        string editCustQuery = "SELECT CustName, SicNaic, CustCity, CustAdd, CustState, CustZip FROM Customer WHERE SubId =" + x;
        string editBroQuery = "SELECT BroName, BroAdd, BroCity, BroState, BroZip, EntityType FROM Broker WHERE SubId =" + x; 
        string editSubQuery = "SELECT Coverage, CurrentCoverage, PrimEx, Retention, EffectiveDate, Commission, Premium, Comments FROM Submission WHERE SubmissionId =" + x;
        string epl = "SELECT Entity, Employees, CA, MI, NY, NJ, Primex, EplLim, EplSir, Premium, Wage, Sublim FROM EPL WHERE SubmissionId =" + x;
        string prof = "SELECT Primex, EO, Limit, Retention, Att, Prem, Sublim, Entity FROM ProfessionalEO WHERE SubmissionId =" + x;
        string crim = "SELECT Entity, Employees, PrimEx, LimA, DedA, PremA, LimitB, DedB, PremB FROM CrimeFidelity WHERE SubmissionId =" + x;
        string fid = "SELECT Entity, PrimEx, Limit, SIR, Att, Premium, Sublim FROM Fiduciary WHERE SubmissionId =" + x;
        string not = "SELECT PrimEx, Coverage, SharedSepLim, TradLim, TradDoSir, EplLim, EplSir, EplPrem, EplSublim FROM NotProfit WHERE SubmissionId =" + x;
        string priv = "SELECT Primex, SharedSepLim, TradLim, TradAtt, TradDoSir, TradPrem, EplLim, EplSir, EplAtt, EplWage, EplPrem, EplInvest, FidLim, FidSir, FidAtt, FidPrem, FidSublim FROM PrivateCompany WHERE SubmissionId =" + x;
        string pub = "SELECT Market, Ticker, TradABC, DIC, Limit, SecuritiesSir, OtherSir, Premium, PrimEx, Att, Sublim FROM PublicDO WHERE SubmissionId =" + x;
        using (SqlConnection editConn = new SqlConnection(connectionString))
        {
            editConn.Open();

            using (SqlCommand CustCommand = new SqlCommand(editCustQuery, editConn))
            {

                SqlDataReader dr = CustCommand.ExecuteReader();
                dr.Read();
                LblCustName.Text = dr.GetString(0);
                LblSicNaic.Text = dr.GetString(1);
                LblCustCity.Text = dr.GetString(2);
                LblCustAddress.Text = dr.GetString(3);
                LblCustState.Text = dr.GetString(4);
                LblCustZip.Text = dr.GetInt32(5).ToString();
                dr.Close();
            }
            using (SqlCommand BroCommand = new SqlCommand(editBroQuery, editConn))
            {
                SqlDataReader dr = BroCommand.ExecuteReader();
                dr.Read();
                LblBroName.Text = dr.GetString(0);
                LblBroAddress.Text = dr.GetString(1);
                LblBroCity.Text = dr.GetString(2);
                LblBroState.Text = dr.GetString(3);
                LblBroZip.Text = dr.GetInt32(4).ToString();
                LblEntity.Text = dr.GetString(5);
                dr.Close();
            }
            using (SqlCommand SubCommand = new SqlCommand(editSubQuery, editConn))
            {
                SqlDataReader dr = SubCommand.ExecuteReader();
                dr.Read();
                LblCoverage.Text = dr.GetInt32(0).ToString();
                LblCurrentCoverage.Text = dr.GetInt32(1).ToString();
                LblPrimEx.Text = dr.GetInt32(2).ToString();
                LblRetention.Text = dr.GetInt32(3).ToString();
                LblEffectDate.Text = dr.GetDateTime(4).ToString();
                LblCommission.Text = dr.GetInt32(5).ToString();
                LblPremium.Text = dr.GetInt32(6).ToString();
                LblComments.Text = dr.GetString(7);
                dr.Close();
                HyperLink1.NavigateUrl = "~/ViewEdit.aspx?SubmissionId=" + x;
            }
                string viewQuery = "SELECT ProductId FROM SubmissionProducts WHERE SubmissionId =" + x;

                SqlCommand viewcmd = new SqlCommand(viewQuery, editConn);

                SqlDataReader drRows = viewcmd.ExecuteReader();
                while (drRows.Read())
                    {
                        switch (drRows.GetInt32(0))
                        {
                            case 1:
                                PanelEplShow.Visible = true;
                                using (SqlCommand eplviewcmd = new SqlCommand(epl, editConn))
                                {
                                    SqlDataReader epldr = eplviewcmd.ExecuteReader();
                                    epldr.Read();
                                    LblEplShowEntity.Text = epldr.GetString(0);
                                    LblEplShowTotalEmpl.Text = epldr.GetInt32(1).ToString();
                                    LblEplShowCalEmpl.Text = epldr.GetInt32(2).ToString();
                                    LblEplShowMichEmpl.Text = epldr.GetInt32(3).ToString();
                                    LblEplShowNyEmpl.Text = epldr.GetInt32(4).ToString();
                                    LblEplShowNjEmpl.Text = epldr.GetInt32(5).ToString();
                                    LblEplShowPrimEx.Text = epldr.GetInt32(6).ToString();
                                    LblEplShowLim.Text = epldr.GetInt32(7).ToString();
                                    LblEplShowSir.Text = epldr.GetInt32(8).ToString();
                                    LblEplShowPrem.Text = epldr.GetInt32(9).ToString();
                                    LblEplShowWage.Text = epldr.GetInt32(10).ToString();
                                    LblEplShowInvestCost.Text = epldr.GetInt32(11).ToString();
                                    epldr.Close();
                                }
                                break;
                            case 2:
                                PanelProfShow.Visible = true;
                                using (SqlCommand profcmd = new SqlCommand(prof, editConn))
                                {
                                    SqlDataReader profdr = profcmd.ExecuteReader();
                                    profdr.Read();
                                    LblProfShowPrimEx.Text = profdr.GetInt32(0).ToString();
                                    LblProfShowType.Text = profdr.GetString(1);
                                    LblProfShowLim.Text = profdr.GetInt32(2).ToString();
                                    LblProfShowRetention.Text = profdr.GetInt32(3).ToString();
                                    LblProfShowAtt.Text = profdr.GetInt32(4).ToString();
                                    LblProfShowPrem.Text = profdr.GetInt32(5).ToString();
                                    LblProfShowSublim.Text = profdr.GetInt32(6).ToString();
                                    LblProfShowEntity.Text = profdr.GetString(7);
                                    profdr.Close();
                                }
                                break;
                            case 3:
                                PanelCrimeShow.Visible = true;
                                using (SqlCommand crimcmd = new SqlCommand(crim, editConn))
                                {
                                    SqlDataReader crimdr = crimcmd.ExecuteReader();
                                    crimdr.Read();
                                    LblCrimeShowEntity.Text = crimdr.GetString(0);
                                    LblCrimeShowEmpl.Text = crimdr.GetInt32(1).ToString();
                                    LblCrimeShowPrimEx.Text = crimdr.GetInt32(2).ToString();
                                    LblCrimeShowLimA.Text = crimdr.GetInt32(3).ToString();
                                    LblCrimeShowDedA.Text = crimdr.GetInt32(4).ToString();
                                    LblCrimeShowPremA.Text = crimdr.GetInt32(5).ToString();
                                    LblCrimeShowLimB.Text = crimdr.GetInt32(6).ToString();
                                    LblCrimeShowDedB.Text = crimdr.GetInt32(7).ToString();
                                    LblCrimeShowPremB.Text = crimdr.GetInt32(8).ToString();
                                    crimdr.Close();
                                }
                                break;
                            case 4:
                                PanelFidShow.Visible = true;
                                using (SqlCommand fidcmd = new SqlCommand(fid, editConn))
                                {
                                    SqlDataReader fiddr = fidcmd.ExecuteReader();
                                    fiddr.Read();
                                    LblFidShowEntity.Text = fiddr.GetString(0);
                                    LblFidShowPrimEx.Text = fiddr.GetInt32(1).ToString();
                                    LblFidShowLim.Text = fiddr.GetInt32(2).ToString();
                                    LblFidShowSir.Text = fiddr.GetInt32(3).ToString();
                                    LblFidShowAtt.Text = fiddr.GetInt32(4).ToString();
                                    LblFidShowPrem.Text = fiddr.GetInt32(5).ToString();
                                    LblFidShowSublim.Text = fiddr.GetInt32(6).ToString();
                                    fiddr.Close();
                                }
                                break;
                            case 5:
                                PanelNotShow.Visible = true;
                                using (SqlCommand notcmd = new SqlCommand(not, editConn))
                                {
                                    SqlDataReader notdr = notcmd.ExecuteReader();
                                    notdr.Read();
                                    LblNotShowPrimEx.Text = notdr.GetInt32(0).ToString();
                                    LblNotShowCov.Text = notdr.GetInt32(1).ToString();
                                    LblNotShowSharedLim.Text = notdr.GetInt32(2).ToString();
                                    LblNotShowTradLim.Text = notdr.GetInt32(3).ToString();
                                    LblNotShowTradSir.Text = notdr.GetInt32(4).ToString();
                                    LblNotShowEplLim.Text = notdr.GetInt32(5).ToString();
                                    LblNotShowEplSir.Text = notdr.GetInt32(6).ToString();
                                    LblNotShowEplPrem.Text = notdr.GetInt32(7).ToString();
                                    LblNotShowSublim.Text = notdr.GetInt32(8).ToString();
                                    notdr.Close();
                                }
                                break;
                            case 6:
                                PanelPrivShow.Visible = true;
                                using (SqlCommand privcmd = new SqlCommand(priv, editConn))
                                {
                                    SqlDataReader privdr = privcmd.ExecuteReader();
                                    privdr.Read();
                                    LblPrivShowPrimEx.Text = privdr.GetInt32(0).ToString();
                                    LblPrivShowSharedLim.Text = privdr.GetInt32(1).ToString();
                                    LblPrivShowTradLim.Text = privdr.GetInt32(2).ToString();
                                    LblPrivShowTradAtt.Text = privdr.GetInt32(3).ToString();
                                    LblPrivShowTradSir.Text = privdr.GetInt32(4).ToString();
                                    LblPrivShowTradPrem.Text = privdr.GetInt32(5).ToString();
                                    LblPrivShowEplLim.Text = privdr.GetInt32(6).ToString();
                                    LblPrivShowEplSir.Text = privdr.GetInt32(7).ToString();
                                    LblPrivShowEplAtt.Text = privdr.GetInt32(8).ToString();
                                    LblPrivShowEplPrem.Text = privdr.GetInt32(9).ToString();
                                    LblPrivShowEplWage.Text = privdr.GetInt32(10).ToString();
                                    LblPrivShowEplSublim.Text = privdr.GetInt32(11).ToString();
                                    LblPrivShowFidLim.Text = privdr.GetInt32(12).ToString();
                                    LblPrivShowFidSir.Text = privdr.GetInt32(13).ToString();
                                    LblPrivShowFidAtt.Text = privdr.GetInt32(14).ToString();
                                    LblPrivShowFidPrem.Text = privdr.GetInt32(15).ToString();
                                    LblPrivShowFidSublim.Text = privdr.GetInt32(16).ToString();
                                    privdr.Close();
                                }
                                break;
                            case 7:
                                PanelPubShow.Visible = true;
                                using (SqlCommand pubcmd = new SqlCommand(pub, editConn))
                                {
                                    SqlDataReader pubdr = pubcmd.ExecuteReader();
                                    pubdr.Read();
                                    LblPubShowMark.Text = pubdr.GetInt32(0).ToString();
                                    LblPubShowTick.Text = pubdr.GetInt32(1).ToString();
                                    LblPubShowTrad.Text = pubdr.GetInt32(2).ToString();
                                    LblPubShowDic.Text = pubdr.GetString(3);
                                    LblPubShowLim.Text = pubdr.GetInt32(4).ToString();
                                    LblPubShowSecSir.Text = pubdr.GetInt32(5).ToString();
                                    LblPubShowAllSir.Text = pubdr.GetInt32(6).ToString();
                                    LblPubShowPrem.Text = pubdr.GetInt32(7).ToString();
                                    LblPubShowPrimEx.Text = pubdr.GetInt32(8).ToString();
                                    LblPubShowAtt.Text = pubdr.GetInt32(9).ToString();
                                    LblPubShowSublim.Text = pubdr.GetInt32(10).ToString();
                                    pubdr.Close();
                                }
                                break;
                            default:
                                break;
                        }
                    }
                drRows.Close();

        }        
    }   
}

【讨论】：