LINQ to Entities不支持指定的类型成员'DateTime' [英] The specified type member 'DateTime' is not supported in LINQ to Entities

问题描述

我正在使用连接器的最新开发版本 - 6.3.3 beta通过VS2010中的Entity Framework 4连接到一个mysql数据库。

我有遵循使用TIMESTAMP列的Linq语句 - createdDate - 在查询中。这是代码：

  int timeThreshold = 5; 
 DateTimeOffset cutoffTime = DateTime.Now.AddMinutes（-timeThreshold）; 
 
使用（var context = new opusismEntities（））
 {
 var unprocessedMessages = from m in context.messages 
其中m.createdDate< = cutoffTime 
选择m; 
 try 
 {
 foreach（var message in unprocessedMessages）
 {
 int gfff = 5; 
} 
} 
 catch（异常e）
 {
 string exceptionString = e.InnerException.ToString（）; 
} 
 
} 
  

CLR抛出以下异常：

MySql.Data.MySqlClient.MySqlException（0x80004005）：命令执行过程中遇到致命错误---> MySql.Data.MySqlClient.MySqlException（0x80004005）：在MySql.Data.Types.MySqlDateTime.MySql.Data.Types.IMySqlValue.WriteValue（MySqlPacket数据包，布尔二值，对象值，Int32长度）\r\中无法序列化日期/时间值。 n在MySql.Data.MySqlClient.MySqlParameter.Serialize（MySqlPacket数据包，布尔二进制，MySqlConnectionStringBuilder设置）\r\\\
在MySql.Data.MySqlClient.Statement.SerializeParameter（MySqlParameterCollection参数，MySqlPacket数据包，字符串parmName）\r \\\
在MySql.Data.MySqlClient.Statement.InternalBindParameters（String sql，MySqlParameterCollection参数，MySqlPacket数据包）\r\\\
在MySql.Data.MySqlClient.Statement.BindParameters（）\r\ （MySql.Data.MySqlClient.Statement.Execute ）\r\\\
在MySql.Data.MySqlClient.MySqlCommand.ExecuteReader（CommandBehavior行为）\r\\\
在MySql.Data.Entity.EFMySqlCommand.ExecuteDbDataReader（CommandBehavior行为）\r\\\
在系统。 Data.Common.DbCommand.ExecuteReader（CommandBehavior行为）\r\\\
在System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands（EntityCommand entityCommand，CommandBehavior行为）

我试图遵循以下链接的建议：
http：/ /bugs.mysql.com/bug.php?id=52550

通过声明一个DateTime而不是DateTimeOffset：

  DateTime cutoffTime = DateTime.Now.AddMinutes（-timeThres保持）; 
 
 ... 
 var unprocessedMessages = from m in context.messages 
其中m.createdDate.DateTime< = cutoffTime 
 select m; 
  

并使用格式.createdDate.DateTime，但实体框架不喜欢它并返回例外：

LINQ to Entities不支持指定的类型成员DateTime

---

这被报告为以前版本的NET / Connector中的错误。

希望GA版本6.3.4可以解决这个问题，但是仍然存在于6.3.3 beta。

解决方案

这是LINQ to Entities issue..it不允许你使用属性/在这个查询中的方法不仅仅是DateTime，而且对于别人也是这样。

获取另一个变量中的值，并在查询中使用该变量，如

DateTime dt = createdDate.DateTime;

或只是删除DateTime ...因为它的价值是一样的...应该摆脱异常。但我不知道你正在尝试实现，虽然...

I am using the latest development version of the connector - 6.3.3 beta to connect to a mysql database via the Entity Framework 4 in VS2010.

I have the following Linq statement which uses a TIMESTAMP column - createdDate - in the query. Here is the code:

        int timeThreshold = 5;
        DateTimeOffset cutoffTime = DateTime.Now.AddMinutes(-timeThreshold);

        using (var context = new opusismEntities())
        {
            var unprocessedMessages = from m in context.messages
                                      where m.createdDate <= cutoffTime
                                      select m;
            try
            {
                foreach (var message in unprocessedMessages)
                {
                    int gfff = 5;
                }
            }
            catch (Exception e)
            {
                string exceptionString = e.InnerException.ToString();
            }

        }

The CLR is throwing the following exception:

"MySql.Data.MySqlClient.MySqlException (0x80004005): Fatal error encountered during command execution. ---> MySql.Data.MySqlClient.MySqlException (0x80004005): Unable to serialize date/time value.\r\n at MySql.Data.Types.MySqlDateTime.MySql.Data.Types.IMySqlValue.WriteValue(MySqlPacket packet, Boolean binary, Object value, Int32 length)\r\n at MySql.Data.MySqlClient.MySqlParameter.Serialize(MySqlPacket packet, Boolean binary, MySqlConnectionStringBuilder settings)\r\n at MySql.Data.MySqlClient.Statement.SerializeParameter(MySqlParameterCollection parameters, MySqlPacket packet, String parmName)\r\n at MySql.Data.MySqlClient.Statement.InternalBindParameters(String sql, MySqlParameterCollection parameters, MySqlPacket packet)\r\n at MySql.Data.MySqlClient.Statement.BindParameters()\r\n at MySql.Data.MySqlClient.Statement.Execute()\r\n at MySql.Data.MySqlClient.PreparableStatement.Execute()\r\n at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)\r\n at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)\r\n at MySql.Data.Entity.EFMySqlCommand.ExecuteDbDataReader(CommandBehavior behavior)\r\n at System.Data.Common.DbCommand.ExecuteReader(CommandBehavior behavior)\r\n at System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior)"

I’ve attempted to follow the advice from the following link: http://bugs.mysql.com/bug.php?id=52550

by declaring a DateTime instead of DateTimeOffset:

DateTime cutoffTime = DateTime.Now.AddMinutes(-timeThreshold);

...
var unprocessedMessages = from m in context.messages
                                      where m.createdDate.DateTime <= cutoffTime
                                      select m;

and use the format .createdDate.DateTime, but Entity Framework doesn’t like it and returns back an exception:

The specified type member 'DateTime' is not supported in LINQ to Entities

---

This was reported as a bug in previous versions of NET/Connector.

Hopefully the GA version 6.3.4 will fix this issue, but it still persists in 6.3.3 beta.

解决方案

Well this is LINQ to Entities issue..it does not allow you to use properties/methods like that in a query...not only for DateTime but for others too.

Get the value in another variable and use that variable in the query like

DateTime dt=createdDate.DateTime;

Or just remove DateTime...because it's value is the same...that should get rid of exception.But I am not sure what you are trying achieve though...

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