Question

我是实体框架和ASP.NET的新手。我正在尝试访问导航属性的属性。但我面临“已经处置了ObjectContext实例”的错误。比我做了一些谷歌，发现它可以由data = db.tblCourses.Include(c => c.tblSection).ToList();修复，但我仍然面临问题。型号：

using System.Data.Entity;
public List<tblCourse> editedCoursesView()
{
    List<tblCourse> data;
    using (enrolmentsystemEntities db = new enrolmentsystemEntities())
    {
        data = db.tblCourses.ToList();
        data = db.tblCourses.Include(c => c.tblSection).ToList();
        return data;
    }
}

tblCourse：

namespace enrolmentSystem.Models
{
    using System;
    using System.Collections.Generic;

    public partial class tblCourse
    {
        public tblCourse()
        {
            this.tblenrolments = new HashSet<tblenrolment>();
        }

        public int CourseId { get; set; }
        public string CourseName { get; set; }
        public int departmentID { get; set; }
        public int TeacherId { get; set; }
        public int CreditHours { get; set; }
        public int SectionId { get; set; }

        public virtual tbldepartment tbldepartment { get; set; }
        public virtual tblteacher tblteacher { get; set; }
        public virtual ICollection<tblenrolment> tblenrolments { get; set; }
        public virtual tblSection tblSection { get; set; }
    }
}

tblRoom：

    namespace enrolmentSystem.Models
{
    using System;
    using System.Collections.Generic;

    public partial class tblRoom
    {
        public tblRoom()
        {
            this.tblSections = new HashSet<tblSection>();
        }

        public int RoomNo { get; set; }
        public string Block { get; set; }
        public int Capacity { get; set; }

        public virtual ICollection<tblSection> tblSections { get; set; }
    }
}

控制器：

[HttpGet]
public ActionResult editCourse()
{
    course c = new course();
    List<tblCourse> data = c.editedCoursesView();
    return View("editCourse", data);    
}

查看：

@model List<enrolmentSystem.Models.tblCourse>
@{
    ViewBag.Title = "editCourse";

}

<h2>Edit Course</h2>
<table border="1">
    <tr style="text-align:center;">
        <td>Course ID</td>
        <td>Course Name</td>
        <td> Course Department ID</td>
        <td> Course Teacher ID</td>
        <td> Course CreditHours</td>
        <td> Course StartTime</td>
        <td> Course EndTime</td>
        <td> MaxCapacity </td>
        <td> Course RoomNo </td>


    </tr>
    @if (Model != null)
    {

        foreach (var i in Model)
        {
            <form action="~/Enrolment/editCourse" method="post">
                <tr>


                    <td>@i.CourseId <input name="id" type="hidden" value="@i.CourseId" /> </td>
                    <td><input type="text" name="name" value="@i.CourseName" required /></td>
                    <td><input type="number" name="dpId" value="@i.departmentID" required /></td>
                    <td><input type="number" name="teacherId" value="@i.TeacherId" required /></td>


                    <td><input type="number" name="creditHours" value="@i.CreditHours" required /></td>
                    <td><input type="text" name="startTime" value="@i.tblSection.startTime" required /></td>
                    <td><input type="text" name="endTime" value="@i.tblSection.endTime" required /></td>
                    <td><input type="number" name="capacity" value="@i.tblSection.tblRoom.Capacity" required /></td>
                    <td><input type="number" name="roomNo" value="@i.tblSection.RoomNo" required /></td>
                    <td>  <input type="submit" value="Update Course" /> </td>


                </tr>
            </form>
        }
    }
</table>

Answer 1

tblRoom可能会导致问题，因为它不包含但在视图中引用。通常，此错误意味着您正在尝试延迟加载某些属性，但已经处理了上下文。

使用.Include(x => x.ApplicationsWithOverrideGroup.NestedProp)或.Include(x => x.Collection.Select(y => y.Property))包含嵌套属性或集合。

在您的情况下使用：

public List<tblCourse> editedCoursesView()
{
    List<tblCourse> data;
    using (enrolmentsystemEntities db = new enrolmentsystemEntities())
    {
        data = db.tblCourses
          .Include(c => c.tblSection)
          .Include(c => c.tblSection.tblRoom)
          .ToList();
        return data;
    }
}

ASP.NET：ObjectContext实例已被释放

1 个答案: