我应该如何使用 ToPagedList 从控制器传递我的查询

Question

实际上我想在我的视图页面中集成分页，为此我正在从下面的代码中检索数据，我正在将这段代码从控制器传递给视图但是我遇到的任何问题都是

 var model = (from sr in db.StudentRequests
                join c in db.Classes
                on sr.ClassId equals c.ClassId
                select new { sr.StudentRequestId,c.ClassName,sr.CreatedOn,sr.Location,sr.PaymentMethod }).ToList().ToPagedList(page ?? 1, 1);           
  return View(model);

我遇到了

的问题

Type : InvalidOperationException
Message : The model item passed into the dictionary is of type 'PagedList.PagedList`1[<>f__AnonymousType3`5[System.Int32,System.String,System.Nullable`1[System.DateTime],System.String,System.String]]', but this dictionary requires a model item of type 'PagedList.IPagedList`1[Student_Tutor.Models.StudentRequest]'.
Source : System.Web.Mvc

我的视角是

@using PagedList;
@using PagedList.Mvc;
@model IPagedList<Student_Tutor.Models.StudentRequest>
    @if (ViewBag.StudentRequest != null)
        { 
          var StudentRequestId = (int)Model.First().StudentRequestId;// Here I am able to get the StudentRequestId 
          var StudentRequestTimecount = StudentRequestTime.Where(d => d.StudentRequestId == StudentRequestId).ToList();
          var TutorStudentRequestcount = TutorStudentRequest.Where(d => d.StudentRequestId == StudentRequestId).ToList();
          @Html.Displayfor(model => model.First().StudentRequestId)// here only text is displaying as StudentRequestId
          @Html.Displayfor(Model => Model.First().CreatedOn)//here only text is diplaying as created on
    }

请解释为什么我会收到此错误？

更新 1

                var model = (from sr in db.StudentRequests
                              join c in db.Classes
                              on sr.ClassId equals c.ClassId
                              select new Studentvm{ StudentRequestId  = sr.StudentRequestId,ClassName= c.ClassName,
                              CreatedOn =Convert.ToDateTime(sr.CreatedOn),Location= sr.Location,PaymentMethod= sr.PaymentMethod })
                              .ToList().ToPagedList(page ?? 1, 1);

                return View(model);

但我收到错误

An exception of type 'System.NotSupportedException' occurred in Student_Tutor.dll but was not handled in user code

Additional information: LINQ to Entities does not recognize the method 'System.DateTime ToDateTime(System.Object)' method, and this method cannot be translated into a store expression.

Answer 1

这部分 LINQ 代码

select new { sr.StudentRequestId,c.ClassName,sr.CreatedOn,sr.Location,sr.PaymentMethod }

这是为您从 LINQ 查询获得的结果集合中的每个项目创建一个匿名对象，并且您正在从中创建一个 PagedList。但是您的视图被强类型化为 PagedList<StudentRequest>

理想的解决方案是创建一个视图模型来表示此视图所需的数据，并将其用于 LINQ 查询的投影部分

public class StudentVm
{
  public int StudentRequestId { set;get;}
  public string ClassName { set;get;}
  public DateTime CreatedOn { set;get;}
  public string Location { set;get;}
}

现在将此视图模型用于您的投影

  select new StudentVm { StudentRequestId  = sr.StudentRequestId,
                         ClassName= c.ClassName,
                         Location = sr.Location,
                         CreatedOn = sr.CreatedOn }

并确保您的视图不是强类型 PagedList<StudentVm>

@using PagedList;
@model PagedList<YourNamespace.StudentVm>

<table>
    @foreach (var item in Model)
    {
        <tr>
            <td>@Html.DisplayFor(a=> item.ClassName)</td>
            <td>@Html.DisplayFor(a=> item.Location)</td>
            <td>@Html.DisplayFor(a=> item.StudentRequestId)</td>
            <td>@Html.DisplayFor(a=> item.CreatedOn)</td>
        </tr>
    }
</table>

另外，从你的问题来看，你并没有真正使用 PagedList。要仅传递项目列表，您不需要将其转换为 PagedList<T> 。您可以简单地从操作方法发送一个 List<StudentVm> 并将您的视图更改为强类型来执行此操作。如果你真的使用它（用于分页），请使用 PagedList

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