Question

我正在阅读Programming Entity Framework, 2nd Edition，在第一章中有一个非常简单的查询：

    private static void QueryContacts()
    {
        using (var context = new SampleEntities())
        {
            var contacts = context.Contacts.Where(c => c.FirstName == "Robert");
            var res = (contacts as ObjectQuery<Contact>).Execute(MergeOption.NoTracking);

            foreach (var contact in res)
            {
                foreach (var address in contact.Addresses)
                {
                    Console.WriteLine("\t{0}", address.City);
                }
            }
        }
        Console.Write("Press Enter...");
        Console.ReadLine();
    }

当我将SQL分析器附加到数据库实例时，我可以看到执行了以下SQL：

SELECT 
[Extent1].[ContactID] AS [ContactID], 
[Extent1].[FirstName] AS [FirstName], 
[Extent1].[LastName] AS [LastName], 
[Extent1].[Title] AS [Title], 
[Extent1].[AddDate] AS [AddDate], 
[Extent1].[ModifiedDate] AS [ModifiedDate]
FROM [dbo].[Contact] AS [Extent1]
WHERE N'Robert' = [Extent1].[FirstName]

但是没有查询地址表的迹象（即使有地址）。

当我附加Entity Framework Profiler时，我可以看到两者：

SELECT [Extent1].[ContactID]    AS [ContactID],
       [Extent1].[FirstName]    AS [FirstName],
       [Extent1].[LastName]     AS [LastName],
       [Extent1].[Title]        AS [Title],
       [Extent1].[AddDate]      AS [AddDate],
       [Extent1].[ModifiedDate] AS [ModifiedDate]
FROM   [dbo].[Contact] AS [Extent1]
WHERE  N'Robert' = [Extent1].[FirstName]

和

SELECT [Extent1].[addressID]     AS [addressID],
       [Extent1].[Street1]       AS [Street1],
       [Extent1].[Street2]       AS [Street2],
       [Extent1].[City]          AS [City],
       [Extent1].[StateProvince] AS [StateProvince],
       [Extent1].[CountryRegion] AS [CountryRegion],
       [Extent1].[PostalCode]    AS [PostalCode],
       [Extent1].[AddressType]   AS [AddressType],
       [Extent1].[ContactID]     AS [ContactID],
       [Extent1].[ModifiedDate]  AS [ModifiedDate]
FROM   [dbo].[Address] AS [Extent1]
WHERE  [Extent1].[ContactID] = 209 /* @EntityKeyValue1 */

您是否知道SQL Server Profiler发生了什么，以便不会捕获对Address表的查询？

由于

Answer 1

宾果！

我选择了所有事件类型，结果发现地址查询可以作为RPC：已完成，而联系人可以作为SQL进行跟踪：BatchCompleted：

exec sp_executesql N'SELECT 
[Extent1].[addressID] AS [addressID], 
[Extent1].[Street1] AS [Street1], 
[Extent1].[Street2] AS [Street2], 
[Extent1].[City] AS [City], 
[Extent1].[StateProvince] AS [StateProvince], 
[Extent1].[CountryRegion] AS [CountryRegion], 
[Extent1].[PostalCode] AS [PostalCode], 
[Extent1].[AddressType] AS [AddressType], 
[Extent1].[ContactID] AS [ContactID], 
[Extent1].[ModifiedDate] AS [ModifiedDate]
FROM [dbo].[Address] AS [Extent1]
WHERE [Extent1].[ContactID] = @EntityKeyValue1',N'@EntityKeyValue1 int',@EntityKeyValue1=220

Answer 2

在循环内部延迟加载期间查询地址。使用Contacts进行单次拍摄会更有效。为此，您需要：

var res = (contacts as ObjectQuery<Contact>).Include("Addresses").Execute(MergeOption.NoTracking);

SQL Server Profiler不会跟踪所有Entity Framework 4查询 - 问题

2 个答案: