1
我有一个ASP.NET MVC Code First站点。我有一个型号Teacher
,它有一个列表Student
s,其中每个都有一个计算属性CompletedTests
。 我越来越想包含的Student
是清单一个ViewModel内访问计算财产CompletedTests
如果出现以下错误:MVC CodeFirst计算属性获取错误“ObjectContext实例处置”
An exception of type 'System.ObjectDisposedException' occurred in EntityFramework.dll but was not handled in user code
Additional information: The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.
老师:
public class Teacher
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Student> Students{ get; set; }
}
学生:
public class Student
{
public int Id { get; set; }
public string Name { get; set; }
public int TeacherId { get; set; }
public virtual Teacher Teacher { get; set; }
public int TotalTests
{
get
{
return Tests.Count;
}
}
public int CompletedTests
{
get
{
return Tests.Count(p => p.IsCompleted);
}
}
public virtual ICollection<Test> Tests{ get; set; }
}
测试:
public class Test
{
public int Id { get; set; }
public int StudentId { get; set; }
public int QuestionsTotal
{
get
{
return Questions.Count;
}
}
public bool IsCompleted
{
get
{
return Questions.Count(q => q.Completed) >= QuestionsTotal;
}
}
public virtual Student Student { get; set; }
public virtual ICollection<Question> Questions{ get; set; }
}
问:
public class Question
{
public int Id { get; set; }
public int TestId { get; set; }
public virtual Question Question { get; set; }
}
HomeViewModel:
public class HomeViewModel
{
public string TeacherName { get; set; }
public int StudentCount { get; set; }
public IEnumerable<Student> Students { get; set; }
}
首页控制器:
public ActionResult Index()
{
var model = new HomeViewModel();
var userId = User.Identity.GetUserId();
using (var context = new ApplicationDbContext())
{
var teacher = context.Teachers.FirstOrDefault(c => c.IdentityId == userId);
if (teacher != null)
{
model.TeacherName = teacher.Name;
model.Students = teacher.Students.ToList();
}
return View(model);
}
}
Index.cshtml部分:
<tbody>
@foreach (var student in Model.Students)
{
<tr>
<td>
@student.Name
</td>
<td>
@(student.CompletedTests + "/" + student.TotalTests)
</td>
</tr>
}
</tbody>
难道有人请指出为什么我在student.CompletedTests
部件上收到处置的实例错误?
我看不到你在哪里得到老师或学生的名字。您只有'Test'中的'Name'字段。 –
对不起,有错的课。它在'Student'上,而不是'Test'。 – Marcus
'teacher.Name'呢? –