DbDataReader，NextResult（）並填充多個表

Question

這個問題是我之前的問題的延續。 在沒有涉及太多細節的情況下，我正在用2個相關的1對多表填充數據集。 所以，我現在的問題是 - 為什么這段代碼運作良好

public DataAgencyR_DataSet SelectOne(int id)
{
    DataAgencyR_DataSet result = new DataAgencyR_DataSet();
    using (DbCommand command = Connection.CreateCommand())
    {
        try
        {               
            command.CommandText = SqlStrings.SelectDataAgencyR_SelectOne();

            var param = ParametersBuilder.CreateByKey(command, "ID_DeclAgenc", id, "ID_DeclAgenc");
            command.Parameters.Add(param);
            Connection.Open();
            using (DbDataReader reader = command.ExecuteReader())
            {
                while (reader.Read())
                {
                    System.Diagnostics.Trace.WriteLine(String.Format("{0}-{1}", reader[0], reader[1]));
                }
                System.Diagnostics.Trace.WriteLine("-------------");
                reader.NextResult();
                while (reader.Read())
                {
                    System.Diagnostics.Trace.WriteLine(String.Format("{0}-{1}", reader[0], reader[1]));
                }
            }

        }
        catch (DbException e)
        {
            Logger.Error(e.Message, e);
            throw new DataAccessException("Error occurs while SelectOne method porcessed", e);
        }
        finally
        {
            if (Connection.State != ConnectionState.Closed)                     Connection.Close();
        }
    }
    return result;
}

public static string SelectDataAgencyR_SelectOne()
{
    return "SELECT a.* FROM t0_DataAgency_R a WHERE a.SetToPartners = 1 AND a.ID_DeclAgenc = @ID_DeclAgenc;" +
                   "SELECT c.* FROM t01_ChoiceParam_R c JOIN t0_DataAgency_R a on a.ID_DeclAgenc = c.ID_DeclAgenc WHERE SetToPartners = 1 AND a.ID_DeclAgenc = @ID_DeclAgenc";
}

而事實並非如此

public DataAgencyR_DataSet SelectOne(int id)
{
    DataAgencyR_DataSet result = new DataAgencyR_DataSet();

    using (DbCommand command = Connection.CreateCommand())
    {
        try
        {               
            command.CommandText = SqlStrings.SelectDataAgencyR_SelectOne();             
            var param = ParametersBuilder.CreateByKey(command, "ID_DeclAgenc", id, "ID_DeclAgenc");
            command.Parameters.Add(param);
            Connection.Open();
            using (DbDataReader reader = command.ExecuteReader())
            {
                result.t0_DataAgency_R.Load(reader);
                reader.NextResult();
                result.t01_ChoiceParam_R.Load(reader);
            }
        }
        catch (DbException e)
        {
            Logger.Error(e.Message, e);
            throw new DataAccessException("Error occurs while SelectOne method porcessed", e);
        }
        finally
        {
            if (Connection.State != ConnectionState.Closed) Connection.Close();
        }
    }
    return result;
}


public static string SelectDataAgencyR_SelectOne()
{
    return "SELECT a.* FROM t0_DataAgency_R a WHERE a.SetToPartners = 1 AND a.ID_DeclAgenc = @ID_DeclAgenc;" +
                   "SELECT c.* FROM t01_ChoiceParam_R c JOIN t0_DataAgency_R a on a.ID_DeclAgenc = c.ID_DeclAgenc WHERE SetToPartners = 1 AND a.ID_DeclAgenc = @ID_DeclAgenc";
}

在第二個例子之后，我只填充了result.t0_DataAgency_R表 - 但不是result.t01_ChoiceParam_R。 為什么會這樣？

提前致謝

Answer 1

DataTable.Load自動將閱讀器推進到下一個結果。 因此，您應該刪除對NextResult的顯式調用。

含義：

using (DbDataReader reader = command.ExecuteReader())
{
    result.t0_DataAgency_R.Load(reader);
    result.t01_ChoiceParam_R.Load(reader);
}

Answer 2

添加DataSet到混合...我們曾經使用SqlDataAdapter並返回一個DataSet但沒有利用任何離線功能等，所以SqlDataReader更適合。 這是填充DataSet的代碼。 發現這總體上快了大約10％。

                Dim s As DataSet = New DataSet()

                Using reader As SqlDataReader = command.ExecuteReader()
                    Dim tables As New List(Of DataTable)
                    Do
                        Dim table As New DataTable()
                        table.Load(reader)
                        tables.Add(table)
                        s.Tables.Add(table)
                    Loop While Not reader.IsClosed

                    s.Load(reader, LoadOption.OverwriteChanges, tables.ToArray())
                End Using