Question

这个问题是我previous的延续。在没有涉及太多细节的情况下，我正在用2个相关的1对多表填充数据集。所以，我现在的问题是 - 为什么这段代码运作良好

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";
}

这不是

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";
}

在第二个例子之后，我只填充了result.t0_DataAgency_R表 - 但不是result.t01_ChoiceParam_R。为什么会如此？

提前致谢

Answer 1

DataTable.Load会自动将读者推向下一个结果。因此，您应该删除对NextResult的明确调用。

含义：

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...我们曾经使用过SqlDataAdapter并返回了一个DataSet但没有利用任何离线功能等，所以SqlDataReader更适合。这是填充DataSet的代码。发现这总体上快了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

DbDataReader，NextResult（）并填充多个表

2 个答案: