EF 5查找分析器

Question

我将EF 5用于我的项目，并使用EntityProfiler进行配置，我看到我使用Find查询生成的sql是：

SELECT TOP (2) [Extent1].[ID]                  AS [ID],
               [Extent1].[TargetID]            AS [TargetID],
               [Extent1].[BranchID]            AS [BranchID],
               [Extent1].[ApplicationStatus]   AS [ApplicationStatus],
               [Extent1].[UserID]              AS [UserID],
               [Extent1].[AssignedOfficer]     AS [AssignedOfficer],
               [Extent1].[AssignedOfficerCRM]  AS [AssignedOfficerCRM],
               [Extent1].[RegistrationDate]    AS [RegistrationDate],
               [Extent1].[DecisionReasons]     AS [DecisionReasons],
               [Extent1].[DecisionExceptionID] AS [DecisionExceptionID],
               [Extent1].[RiskComment]         AS [RiskComment],
               [Extent1].[CESInformed]         AS [CESInformed],
               [Extent1].[IsCommited]          AS [IsCommited]
FROM   [dbo].[Applications] AS [Extent1]
WHERE  [Extent1].[ID] = '900100' /* @p0 */

调用的代码是：

 public T GetByID(object primaryKey)
        {
            return DB.Set<T>().Find(primaryKey);
        }

所以我的questin是为什么生成的sql是Select Top（2）

Answer 1

执行Select Top (2)因为DBSet在内部SingleOrDefault()（请参阅here方法FindInStore）使用Find方法来执行查询。

这可以确保，如果返回2个结果，则抛出异常，因为SingleOrDefault定义它只需要一个结果或没有结果。

Select Top (1)生成为您使用FirstOrDefault（）的Sql。