MySQL Reader 立即关闭

Question

我有一个递归填充列表的方法。首先它选择父项，然后使用外键选择它可能拥有的任何子项。它可以很好地选择父项，但是当它开始选择子项时，就是 Reader 无故关闭的时候。

我已经在调试器中完成了它，我看不出它要关闭的原因。搜索参数有效，搜索 returns 项（我手动检查过），并且 Reader 处于活动状态。然而不知为何，一打开就关闭，没有任何错误。

连接字符串有效
Reader有效
搜索参数有效
命令 returns 结果（我专门测试了这个 - WHERE 1 = 1 AND SE.ParentSE = 4;"; 有超过 10 个结果）

不知道怎么回事？

try
{
    using (MySqlConnection connection = new MySqlConnection(GetConnectionString()))
    {
        connection.Open();

        using (MySqlCommand command = connection.CreateCommand())
        {
            command.CommandText = @"SELECT 
                                    SE.SEId,
                                    SE.Name,
                                    SE.Status,
                                    SE.Description,
                                    SE.ParentME AS ParentMEId,
                                    SE.ParentSE AS ParentSEId,
                                    SE.Comments AS Comments,
                                    SE.Removed AS Removed,
                                    SE.SupplierId AS SupplierId,
                                    TC.TerminalCount AS TerminalCount,
                                    SE2.Name AS ParentSE,
                                    ME.EquipmentNumber AS ParentME,
                                    D.DSId AS DataSheet,
                                    D.DSType AS DataSheetType,
                                    C.Code AS EquipmentType,
                                    C.Description AS TypeDescription,
                                    C.CodeType AS TypeDiscipline,
                                    SE.EquipmentType AS EquipTypeId,
                                    SE3.SEId AS SE3Id,
                                    SE4.SEId AS SE4Id,
                                    SE5.SEId AS SE5Id,
                                    SE6.SEId AS SE6Id,
                                    SE2.ParentME AS ME2Id,
                                    SE3.ParentME AS ME3Id,
                                    SE4.ParentME AS ME4Id,
                                    SE5.ParentME AS ME5Id,
                                    SE6.ParentME AS ME6Id,
                                    PAC.UDCId AS AreaCodeId,
                                    PAC.Code AS AreaCode,
                                    PAC.Description AS AreaCodeDescription
                                FROM SubEquipment SE
                                LEFT  JOIN DataSheet D ON SE.SEId = D.SEId
                                LEFT JOIN (SELECT SEId, COUNT(*) as TerminalCount FROM Terminal GROUP BY SEId) TC ON SE.SEId = TC.SEId
                                LEFT JOIN SubEquipment SE2 ON SE.ParentSE = SE2.SEId
                                LEFT JOIN MajorEquipment ME ON SE.ParentME = ME.MEId
                                LEFT JOIN UserDefinedCode C ON C.UDCId = SE.EquipmentType
                                LEFT JOIN SubEquipment SE3 ON SE2.ParentSE = SE3.SEId
                                LEFT JOIN SubEquipment SE4 ON SE3.ParentSE = SE4.SEId
                                LEFT JOIN SubEquipment SE5 ON SE4.ParentSE = SE5.SEId
                                LEFT JOIN SubEquipment SE6 ON SE5.ParentSE = SE6.SEId
                                INNER JOIN MajorParentage MP ON SE.SEId = MP.SEId
                                INNER JOIN MajorEquipment MEU ON MP.MEId = MEU.MEId
                                INNER JOIN UserDefinedCode PAC ON MEU.PACId = PAC.UDCId
                                LEFT JOIN ComponentStatus CS1 ON CS1.StatusName = SE.Status
                                WHERE 1 = 1"
                                // " AND SE.ParentSE = @SEParentId"                                    
                                // @SEParentId = 4
                                + parentSearch
                                + ";";

            command.Parameters.AddWithValue("@PACId", areaCodeId);
            command.Parameters.AddWithValue("@AreaCode", areaCode.Cipher());
            command.Parameters.AddWithValue("@ETId", equipmentTypeId);
            command.Parameters.AddWithValue("@EquipmentType", equipmentType.Cipher());
            command.Parameters.AddWithValue("@EquipmentNumber", equipmentNumber.Cipher());
            command.Parameters.AddWithValue("@Description", description.Cipher());
            command.Parameters.AddWithValue("@Comments", comments.Cipher());
            command.Parameters.AddWithValue("@TypeDiscipline", typeDiscipline);
            command.Parameters.AddWithValue("@MEParentId", parentMEId);
            command.Parameters.AddWithValue("@MEParent", parentMENumber.Cipher());
            command.Parameters.AddWithValue("@SEParentId", parentSEId);
            command.Parameters.AddWithValue("@SEParent", parentSENumber.Cipher());
            command.Parameters.AddWithValue("@SEId", excludeSEId);
            command.Parameters.AddWithValue("@Status", status.Cipher());

            using (MySqlDataReader reader = command.ExecuteReader())
            {
                // Read all the results and populate a model with them.
                while (reader.Read())
                {
                    // Do stuff...
                }
                // Finished reading the results
                if (!reader.IsClosed)
                    reader.Close();
            }
        }

        // Finished with the connection
        if (connection.State == System.Data.ConnectionState.Open)
            connection.Close();
    }
}
catch (MySqlException e)
{
    ShowMySQLError(e, 4417);
}

Answer 1

找到了。

在整个程序的多个地方都使用了此方法；但出于某种原因，只有 this 调用意外关闭了 Reader。仔细检查 - reader 的属性显示它没有行：HasRows = false。这意味着查询有问题。

我又看了看，发现问题是一个被忽略的参数（我为了这个问题修剪了它——我认为没有必要）。有一些默认的 boolean 参数，其中一个设置为 true，导致查询 return 一个空结果。

故事的寓意：了解您的代码在做什么！

MySQL Reader 立即关闭

MySQL Reader closing immediately

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