为什么我的解决方案中没有AddObject（）方法？

Question

我修改了this ContosoUniversity tutorial，现在我正在尝试使用AutoMapper来映射对象到对象。

这是我的ModelView：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;
using SchoolIn.Models;

namespace SchoolIn.ViewModels
{
public class InstructorIndexData
{

    public IEnumerable<Instructor> Instructors { get; set; }
    public IEnumerable<Course> Courses { get; set; }
    public IEnumerable<Enrollment> Enrollments { get; set; }
    public IEnumerable<Student> Students { get; set; }
    public IEnumerable<Assignment> Assignments { get; set; }


}
}

这是视图

@model SchoolIn.ViewModels.InstructorIndexData

@using SchoolIn.Models
@{
ViewBag.Title = "Index";
}


@using (Html.BeginForm("ClassAttendance", "Attendance", new { currentDate = day, id = @ViewBag.ID, teacher = HttpContext.Current.Session["sTeacher"], courseID =     HttpContext.Current.Session["sCourseID"] }, FormMethod.Post))

{
    var wekdys = new Enrollment(); @*had too create this to have access to the dropdownList*@
        @Html.DropDownList("weekDays", wekdys.WeekDays.Select(s => new    SelectListItem { Text = s.ToString(), Value = s.ToString() }))

@Html.ValidationSummary(true)
<p></p>
 <Input Type ="submit" Value="ClassAttendance"/>
<p>

@Html.ActionLink("Create Todays Attendance", "Create")
</p>




<p>
@Html.ActionLink("Create New", "Create")
</p>


<h3>  
    Students Enrolled in @ViewBag.teacherName's @ViewBag.courseTitle Course</h3>  
<table>  
    <tr>  
    <th>View Student Report</th> 
        <th>First Name</th>  
        <th>Last Name</th> 
        <th>Grade</th>  
        <th>Attendance Code</th>  
         <th>Class Day</th> 
    </tr>  
    @foreach (var item in Model.Enrollments)
    {  
        <tr>  
         <td>  

                @Html.ActionLink("Report", "UpdateAttendance", "Attendance", new  { grade=item.Grade, studentFirstName = item.Student.FirstMidName, studentLastName = item.Student.LastName, courseTitle = item.Course.Title, teacher =    @ViewBag.teacherName }, null)


            </td> 

            <td>  
            @Html.EditorFor(modelItem=>item.Student.FirstMidName)

            </td>  
            <td>  
              @Html.EditorFor(modelItem=>item.Student.LastName)

            </td> 


           <td>

                @Html.EditorFor(modelItem =>item.Grade) 

            </td>
             <td>
                @Html.DropDownList("attendanceCode", item.attendanceCode.Select(s => new SelectListItem { Text = s.ToString(), Value = s.ToString() }))
                @*Html.EditorFor(modelItem =>item.attendanceCode)*/*@


            </td>  
            <td>  


            @Html.EditorFor(modelItem=>item.classDays)

            </td>
        </tr>  

    }  

</table>  

}

这是我控制器中遇到问题的方法。我正在尝试使用this example：

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Objects;
using System.Data.Entity;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using SchoolIn.Models;
using SchoolIn.ViewModels;

namespace SchoolIn.Controllers
{ 
public class AttendanceController : Controller
{
    private SchoolInDB db = new SchoolInDB();

代码在这里......

[HttpPost]
    public ActionResult ClassAttendance(InstructorIndexData viewModel)
    {


        if (ModelState.IsValid)
        {

            AutoMapper.Mapper.CreateMap<AttendanceData, Assignment>();
            AutoMapper.Mapper.CreateMap<AttendanceData, Enrollment>();
            AutoMapper.Mapper.CreateMap<AttendanceData, Student>();
            AutoMapper.Mapper.CreateMap<AttendanceData, Instructor>();

            Instructor newInstructor = new Instructor();
            Student newStudent = new Student();
            Assignment newAssignment = new Assignment();
            Enrollment newEnrollment = new Enrollment();

            AutoMapper.Mapper.Map(viewModel, newInstructor );
            AutoMapper.Mapper.Map(viewModel, newStudent);
            AutoMapper.Mapper.Map(viewModel, newEnrollment);
            AutoMapper.Mapper.Map(viewModel, newAssignment);

            db.Assignments.AddObject(newAssignment).;

            db.SaveChanges();
            return RedirectToAction("Index");
        }

                   return View();
    }

当我尝试db.Assignment.AddObject(newAssignment);时，AddObject方法无法使用。

我用错了吗？为什么AddObject没有AddObject()可用？