填充IEnumerable<；类别>；使用JSON结果

我以前在AdminController中有以下代码行，它成功地从课程中返回了相关小节的列表：

[AcceptVerbs(HttpVerbs.Get)]
public JsonResult GetCourseSections(int courseID)
{ 
  var Sections = dbcontext.CourseSection.Where(cs => cs.CourseID.Equals(courseID)).Select(x => new
  {            
    sectionID = x.CourseSectionID,
    sectionTitle = x.Title
  );
  return Json(Sections, JsonRequestBehavior.AllowGet);
}

我被告知将其从控制器中删除，因为调用dbcontext是一种不好的做法，所以我将其移动到AdminViewModel。在我的AdminViewModel中，我有一个变量public List CourseSectionList{get；set；}，我正试图用JSON请求细节填充这个变量。我的代码如下：

AdminViewModel

public void GetCourseSectionDetails(int courseID)
{
  var Sections = dbcontext.CourseSection.Where(cs => cs.CourseID.Equals(courseID)).Select(x => new CourseSection
  {
    CourseSectionID = x.CourseSectionID,
    Title = x.Title
  });
  this.CourseSectionList = Sections.ToList();
}

public void GetCourseSectionDetails(int courseID)
    {
        this.CourseSectionList = dbcontext.CourseSection.AsEnumerable().Where(cs => cs.CourseID.Equals(courseID)).Select(x => new CourseSection
        {
            CourseSectionID = x.CourseSectionID,
            Title = x.Title
        }).ToList();
    }

AdminController

[AcceptVerbs(HttpVerbs.Get)]
public JsonResult GetCourseSections(int courseID)
{ 
  avm.GetCourseSectionDetails(courseID);
  var Sections = avm.CourseSectionList.Where(cs => cs.CourseID.Equals(courseID)).Select(x => new
  {            
    sectionID = x.CourseSectionID,
    sectionTitle = x.Title
  });
  System.Diagnostics.EventLog.WriteEntry("Application", "JSON=" + Sections.ToList(), System.Diagnostics.EventLogEntryType.Error);
  return Json(Sections, JsonRequestBehavior.AllowGet);
}

[AcceptVerbs(HttpVerbs.Get)]
    public JsonResult GetCourseSections(int courseID)
    {             
        var sections = avm.CourseSectionList;
        return Json(sections, JsonRequestBehavior.AllowGet);
    }

---

我收到错误无法在LINQ to Entities查询中构造实体或复杂类型“MetaLearning.Data.CourseSection”。如何使用节填充此.CourseSectionList变量？

您不需要在控制器中重复相同的代码，而是直接将列表传递给视图

尽管如此，我还是要告诉您，在视图模型中放置数据访问代码比将其保存在控制器中更糟糕。我建议您使用特定的DAL层：

public interface IRepository
{
    public IList<CourseSection> GetSections(int courseID);
}

---

正如错误消息所指出的，您不能在

linq to entities

中使用

.Select(m => new <Entity>{bla bla})

你可以找到一些很好的解释，解释为什么这是不可能的

编辑：

如果只想检索实体的某些属性，而不想使用DTO，也可以这样做：

return ctx
        .CourseSection
         .Where(cs => cs.CourseID.Equals(courseID))
         //use an anonymous object to retrieve only the wanted properties
         .Select(x => new 
                {
                    c= x.CourseSectionID,
                    t= x.Title,
                })
         //enumerate, good bye linq2entities
         .ToList()
         //welcome to linq2objects
         .Select(m => new CourseSection {
                     CourseSectionID = m.c,
                     Title = m.t,
          })
          .ToList();

---

我以达林的回答为指导，做了如下工作：

视图模型

public void GetCourseSectionDetails(int courseID)
{
  var Sections = dbcontext.CourseSection.Where(cs => cs.CourseID.Equals(courseID)).Select(x => new CourseSection
  {
    CourseSectionID = x.CourseSectionID,
    Title = x.Title
  });
  this.CourseSectionList = Sections.ToList();
}

public void GetCourseSectionDetails(int courseID)
    {
        this.CourseSectionList = dbcontext.CourseSection.AsEnumerable().Where(cs => cs.CourseID.Equals(courseID)).Select(x => new CourseSection
        {
            CourseSectionID = x.CourseSectionID,
            Title = x.Title
        }).ToList();
    }

控制器

[AcceptVerbs(HttpVerbs.Get)]
public JsonResult GetCourseSections(int courseID)
{ 
  avm.GetCourseSectionDetails(courseID);
  var Sections = avm.CourseSectionList.Where(cs => cs.CourseID.Equals(courseID)).Select(x => new
  {            
    sectionID = x.CourseSectionID,
    sectionTitle = x.Title
  });
  System.Diagnostics.EventLog.WriteEntry("Application", "JSON=" + Sections.ToList(), System.Diagnostics.EventLogEntryType.Error);
  return Json(Sections, JsonRequestBehavior.AllowGet);
}

[AcceptVerbs(HttpVerbs.Get)]
    public JsonResult GetCourseSections(int courseID)
    {             
        var sections = avm.CourseSectionList;
        return Json(sections, JsonRequestBehavior.AllowGet);
    }

---

很好的重构建议。那么这就行不通了？抱歉，我没有机会在我的开发机器上试用