在EF 5，MVC 4无法检索导航性能数据 [英] can not retrieve data of navigation properties in EF 5, MVC 4

问题描述

我有以下PersonelInCourse实体：

I have the following PersonelInCourse entity:

public partial class PersonnelInCourse
{
    public int ID { get; set; }
    public string PersonnelID { get; set; }
    public string CourseID { get; set; }
    public int HoursInCourse { get; set; }
    public byte IsApproved { get; set; }
    public byte IsPassed { get; set; }
    public Nullable<int> RewardDetailID { get; set; }
    public string RejectReason { get; set; }
    public string FailReason { get; set; }

    public virtual Course Course { get; set; }
    public virtual RewardDetail RewardDetail { get; set; }
    public virtual Personnel Personnel { get; set; }
}

我插入这样的数据，它有没有问题：

I insert data like this and it has no problem:

...
PersonnelInCourse p = new PersonnelInCourse();
p.CourseID = id;
p.PersonnelID = User.Identity.Name;
p.HoursInCourse = 0;
p.IsApproved = 0;
p.IsPassed = 0;            
db.PersonnelInCourses.Add(p);
try
{
    db.SaveChanges();
}
...

我尝试的地方像下面这样检索该信息。但是，这会导致一个例外，我发现所有的导航属性都为空，所以异常抛出：

I try to retrieve this info somewhere like the following. However, this causes an exception and I found out that all of navigation properties are null, so the exception throws:

@{    
var psic = new Models.PtDbContext().PersonnelInCourses.Where(p => p.CourseID == Model.ID);
var c = new Models.PtDbContext().Courses.Find(Model.ID);
int i = 1;
} // these all are ok.
...

@foreach (var p in psic)
{
    <tr style="border-bottom: 1px dotted black;">
        <td>@i.ToString()</td>
        <td>@string.Concat(p.Personnel.FirstName, " ", p.Personnel.LastName)</td> 
    //the exception throws from here, because the navigation property Personnel is null, and all other navPrs also are null.
        <td>@p.Personnel.Post.PostName</td>
        <td>@p.PersonnelID</td>
    </tr>

    i++;
}

我如何能实现我想要什么？哪里是我的错？

How can I achieve what I want? Where is my mistake?

推荐答案

找到了！ （根据@Liel的意见）：

Found it! (based on comments of @Liel):

var psic = new jqPersonnelTraining.Models.PtDbContext().PersonnelInCourses
    .Include("Personnel").Include("Personnel.Post").Where(p => p.CourseID == Model.ID);

亲爱Liel，必须添加 .INCLUDE（）在。凡（） ...非常感谢为你的提示。

dear Liel, you must add .Include() before .Where() ... Thanks a lot for your tips.

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