包括（）在LINQ to Entities查询 [英] Include() in LINQ to Entities query

问题描述

我在我的ASP.NET MVC 3项目以下型号：

I have the following models in my ASP.NET MVC 3 project:

public class Task
{
    public int Id { get; set; }
    public DateTime CreatedOn { get; set; }
    public TaskStatus Status { get; set; }
}

public class TaskStatus
{
    public int Id { get; set; }
    public string Description { get; set; }
}

有关参考，这里是我的的DbContext 类：

For reference, here is my DbContext class:

public class TaskManagerSets : DbContext
{
    public DbSet<Task> TaskSet { get; set; }
    public DbSet<TaskStatus> TaskStatusSet { get; set; }
}    

然后我有一个列表的行动我的 TaskController

TaskManagerSets dbcontext = new TaskManagerSets();
public ActionResult List()
{
    var tasks = from tsk in dbcontext.TaskSet.Include("TaskStatusSet")
                select tsk;
    return View(tasks.ToList());
}

最后，我有任务列表查看：

Finally I have the Task List View:

 @model IEnumerable<TaskManager.Models.Task>

 <ul>
 @foreach (var tsk in Model) 
 { 
    <li>@tsk.Id | @tsk.CreatedOn | @tsk.Status.Description</li> 
 } 
 </ul>

当我执行我的项目，我收到以下错误：

When I execute my project I get the following error:

指定的include路径是无效的。该的EntityType'codeFirstNamespace.Task'没有名为'TaskStatus声明导航属性。

A specified Include path is not valid. The EntityType 'CodeFirstNamespace.Task' does not declare a navigation property with the name 'TaskStatus'.

问题肯定是在包含（TaskStatusSet）但我应该怎么解决这个问题？

The problem is definitely on the Include("TaskStatusSet") but how should I fix this?

推荐答案

在任务类导航属性名称是状态。所以，你将不得不使用：

The navigation property name in your Task class is Status. So, you would have to use:

var tasks = from tsk in dbcontext.TaskSet.Include("Status")
            select tsk;

但因为你是用的DbContext API一个更好的选择是使用类型安全的过载工作包括：

But since you are working with the DbContext API a better option is to use the type-safe overload of Include:

using System.Data.Entity;
// You must add a using statement for this namespace to have the following 
// lambda version of Include available

//...

var tasks = from tsk in dbcontext.TaskSet.Include(t => t.Status)
            select tsk;

您将获得智能感知和编译时检查，这有助于避免使用错误的字符串像你有问题。

You will get Intellisense and compile-time checks which helps to avoid issues with wrong strings like you had.

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