当我从数据库检索包括某些子项（通过 .Include），并随机排序时，EF给出了一个意外的结果.. 它创建/克隆了额外的项。
为了更好地解释，我创建了一个简单的EF CodeFirst项目来重现这个问题。首先，我将为此项目提供代码。
该项目
创建一个基本的MVC3项目，并通过Nuget添加EntityFramework.SqlServerCompact包。
这会添加以下软件包的最新版本：
- EntityFramework v4.3.0
- SqlServerCompact v4.0.8482.1
- EntityFramework.SqlServerCompact v4.1.8482.2
- WebActivator v1.5
模型和DbContext
using System.Collections.Generic;
using System.Data.Entity;
namespace RandomWithInclude.Models
{
public class PeopleContext : DbContext
{
public DbSet<Person> Persons { get; set; }
public DbSet<Address> Addresses { get; set; }
}
public class Person
{
public int ID { get; set; }
public string Name { get; set; }
public virtual ICollection<Address> Addresses { get; set; }
}
public class Address
{
public int ID { get; set; }
public string AdressLine { get; set; }
public virtual Person Person { get; set; }
}
}
数据库设置和种子数据: EF.SqlServerCompact.cs
using System.Collections.Generic;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using RandomWithInclude.Models;
[assembly: WebActivator.PreApplicationStartMethod(typeof(RandomWithInclude.App_Start.EF), "Start")]
namespace RandomWithInclude.App_Start
{
public static class EF
{
public static void Start()
{
Database.DefaultConnectionFactory = new SqlCeConnectionFactory("System.Data.SqlServerCe.4.0");
Database.SetInitializer(new DbInitializer());
}
}
public class DbInitializer : DropCreateDatabaseAlways<PeopleContext>
{
protected override void Seed(PeopleContext context)
{
var address1 = new Address {AdressLine = "Street 1, City 1"};
var address2 = new Address {AdressLine = "Street 2, City 2"};
var address3 = new Address {AdressLine = "Street 3, City 3"};
var address4 = new Address {AdressLine = "Street 4, City 4"};
var address5 = new Address {AdressLine = "Street 5, City 5"};
context.Addresses.Add(address1);
context.Addresses.Add(address2);
context.Addresses.Add(address3);
context.Addresses.Add(address4);
context.Addresses.Add(address5);
var person1 = new Person {Name = "Person 1", Addresses = new List<Address> {address1, address2}};
var person2 = new Person {Name = "Person 2", Addresses = new List<Address> {address3}};
var person3 = new Person {Name = "Person 3", Addresses = new List<Address> {address4, address5}};
context.Persons.Add(person1);
context.Persons.Add(person2);
context.Persons.Add(person3);
}
}
}
控制器：HomeController.cs
using System;
using System.Data.Entity;
using System.Linq;
using System.Web.Mvc;
using RandomWithInclude.Models;
namespace RandomWithInclude.Controllers
{
public class HomeController : Controller
{
public ActionResult Index()
{
var db = new PeopleContext();
var persons = db.Persons
.Include(p => p.Addresses)
.OrderBy(p => Guid.NewGuid());
return View(persons.ToList());
}
}
}
视图：Index.cshtml
@using RandomWithInclude.Models
@model IList<Person>
<ul>
@foreach (var person in Model)
{
<li>
@person.Name
</li>
}
</ul>
就这些，你的应用程序应该编译:)
SELECT
[Project1].[ID] AS [ID],
[Project1].[Name] AS [Name],
[Project1].[C2] AS [C1],
[Project1].[ID1] AS [ID1],
[Project1].[AdressLine] AS [AdressLine],
[Project1].[Person_ID] AS [Person_ID]
FROM ( SELECT
NEWID() AS [C1],
[Extent1].[ID] AS [ID],
[Extent1].[Name] AS [Name],
[Extent2].[ID] AS [ID1],
[Extent2].[AdressLine] AS [AdressLine],
[Extent2].[Person_ID] AS [Person_ID],
CASE WHEN ([Extent2].[ID] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C2]
FROM [People] AS [Extent1]
LEFT OUTER JOIN [Addresses] AS [Extent2] ON [Extent1].[ID] = [Extent2].[Person_ID]
) AS [Project1]
ORDER BY [Project1].[C1] ASC, [Project1].[ID] ASC, [Project1].[C2] ASC
解决方法
- 如果我从查询中删除
.Include(p =>p.Addresses)，一切都正常。但是，未加载地址并且每次访问该集合时都会向数据库发出新的调用。 - 我可以先从数据库获取数据，然后通过在 .OrderBy.. 前添加 .ToList() 来随机化，就像这样：
var persons = db.Persons.Include(p => p.Addresses).ToList().OrderBy(p => Guid.NewGuid());
有人有任何想法为什么会发生这种情况吗？
这可能是 SQL 生成中的错误吗？
OrderBy不是在父实体的属性上，就会发生荒谬的情况。 - Slauma