Question

我正在使用ViewBag来帮助我对在课程列表中找到的学生列表进行排序。我已经读过ViewBag应该不惜一切代价避免尝试构建一个合适的MVC项目。

当查看以下代码生成的页面时，可以通过各种方式对学生列表进行排序（按名字分类，按字母分类的姓氏，注册日期等），并查看仅限制每页学生人数。

我不知道如何翻译我的代码以使用ViewModel代替我当前的设计。

我使用以下代码：

模特（学生）：

public class Student
{
    public int StudentID { get; set; }
    public string LastName { get; set; }
    public string FirstMidName { get; set; }
    public string Email { get; set; }
    public DateTime EnrollmentDate { get; set; } 
    public virtual ICollection<Enrollment> Enrollments { get; set; }
}

模型（注册）：

public class Enrollment
{
    public int EnrollmentID { get; set; }
    public int CourseID { get; set; }
    public int StudentID { get; set; }
    public string Grade { get; set; } // pass, fail, incomplete
    public virtual Course Course { get; set; } 
    public virtual Student Student { get; set; } 
}

（我也有一个课程模型，但下面的控制器没有直接引用它，所以我在这里省略它 - 如果有必要显示它的详细信息，请告诉我。）

控制器：

public class StudentController : Controller
{
    private SchoolContext db = new SchoolContext();

    //
    // GET: /Student/

    public ViewResult Index(string sortOrder, string currentFilter, string searchString, int? page)
    {
        ViewBag.CurrentSort = sortOrder;
        ViewBag.NameSortParm = String.IsNullOrEmpty(sortOrder) ? "Name desc" : "";
        ViewBag.DateSortParm = sortOrder == "Date" ? "Date desc" : "Date";
        ViewBag.FNameSortParm = sortOrder == "FName" ? "FName desc" : "FName";
        ViewBag.EmailSortParm = sortOrder == "Email" ? "Email desc" : "Email";

        if (Request.HttpMethod == "GET")
        {
            searchString = currentFilter;
        }
        else
        {
            page = 1;
        }
        ViewBag.CurrentFilter = searchString;

        var students = from s in db.Students
                       select s;
        if (!String.IsNullOrEmpty(searchString))
        {
            students = students.Where(s => s.LastName.ToUpper().Contains(searchString.ToUpper())
                                   || s.FirstMidName.ToUpper().Contains(searchString.ToUpper()));
        }
        switch (sortOrder)
        {
            case "Name desc":
                students = students.OrderByDescending(s => s.LastName);
                break;
            case "Date":
                students = students.OrderBy(s => s.EnrollmentDate);
                break;
            case "Date desc":
                students = students.OrderByDescending(s => s.EnrollmentDate);
                break;
            case "FName":
                students = students.OrderBy(s => s.FirstMidName);
                break;
            case "FName desc":
                students = students.OrderByDescending(s => s.FirstMidName);
                break;
            case "Email":
                students = students.OrderBy(s => s.Email);
                break;
            case "Email desc":
                students = students.OrderByDescending(s => s.Email);
                break;
            default:
                students = students.OrderBy(s => s.LastName);
                break;
        }
        int pageSize = 4;
        int pageNumber = (page ?? 1);
        return View(students.ToPagedList(pageNumber, pageSize));
    }

我的观点：

@model PagedList.IPagedList<MVCAppName.Models.Student>

@{
    ViewBag.Title = "Students";
}

<h2>Students</h2>

<p>
    @Html.ActionLink("Create New", "Create")
</p>
@using (Html.BeginForm())
{
    <p>
        Find by name: @Html.TextBox("SearchString", ViewBag.CurrentFilter as string) &nbsp;
        <input type="submit" value="Search" /></p>
}
<table>
    <tr>
    <th></th>
    <th>
        @Html.ActionLink("Last Name", "Index", new { sortOrder = ViewBag.NameSortParm, currentFilter = ViewBag.CurrentFilter })
    </th>
    <th>
        @Html.ActionLink("First Name", "Index", new { sortOrder = ViewBag.FNameSortParm, currentFilter = ViewBag.CurrentFilter })
    </th>
    <th>
        @Html.ActionLink("Email", "Index", new { sortOrder = ViewBag.EmailSortParm, currentFilter = ViewBag.CurrentFilter })
    </th>
    <th>
        @Html.ActionLink("Enrollment Date", "Index", new { sortOrder = ViewBag.DateSortParm, currentFilter = ViewBag.CurrentFilter })
    </th>
</tr>

@foreach (var item in Model) {
    <tr>
        <td>
            @Html.ActionLink("Edit", "Edit", new { id=item.StudentID }) |
            @Html.ActionLink("Details", "Details", new { id=item.StudentID }) |
            @Html.ActionLink("Delete", "Delete", new { id=item.StudentID })
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.LastName)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.FirstMidName)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.Email)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.EnrollmentDate)
        </td>
    </tr>
}

</table>

<div>
    Page @(Model.PageCount < Model.PageNumber ? 0 : Model.PageNumber)
    of @Model.PageCount
    &nbsp;
    @if (Model.HasPreviousPage)
    {
        @Html.ActionLink("<<", "Index", new { page = 1, sortOrder = ViewBag.CurrentSort, currentFilter=ViewBag.CurrentFilter  })
        @Html.Raw("&nbsp;");
        @Html.ActionLink("< Prev", "Index", new { page = Model.PageNumber - 1, sortOrder = ViewBag.CurrentSort, currentFilter=ViewBag.CurrentFilter  })
    }
    else
    {
        @:<<
        @Html.Raw("&nbsp;");
        @:< Prev
    }
    &nbsp;
    @if (Model.HasNextPage)
    {
        @Html.ActionLink("Next >", "Index", new { page = Model.PageNumber + 1, sortOrder = ViewBag.CurrentSort, currentFilter=ViewBag.CurrentFilter  })
        @Html.Raw("&nbsp;");
        @Html.ActionLink(">>", "Index", new { page = Model.PageCount, sortOrder = ViewBag.CurrentSort, currentFilter=ViewBag.CurrentFilter  })
    }
    else
    {
        @:Next >
        @Html.Raw("&nbsp;")
        @:>>
    }
</div>

Answer 1

控制器应该处理排序，视图只显示数据。你已经这样做了，所以你只需要定义视图模型，这个模型可以放在ViewBag中。

public class ShowStudentsModel
{
    public string CurrentSort {get;set;}
    public string NameSortParm {get;set;}
      //and so on... you create a property for each property set in the ViewBag
    public IEnumerable<Student> Students {get;set;}
}

然后在视图中

@model ShowStudentsModel

@foreach(var item in Model.Students)
{
      //html code
  }

Answer 2

我认为最好的方法是继承你正在使用的PagedList.IPagedList<T>并在那里添加排序顺序。所以在你的控制器结束时你会有这个：

    return View(students.ToPagedList(pageNumber, pageSize, sortOrder));

但如果您不愿意这样做，那么您可以简单地创建一个新的ViewModel类来保存PagedList（您当前的模型）以及您需要的补充数据（即您的排序顺序）。

    return View(new SortedStudents
    {
        Students = students.ToPagedList(pageNumber, pageSize);
        SortOrder = sortOrder
    });

SortedStudents定义如下：

public class SortedStudents
{
    public PagedList.IPagedList<MVCAppName.Models.Student> Students { get; set; }
    public string SortOrder { get; set; }
}

Answer 3

你可以围绕学生班制作一个包装

public class StudentWrapper
{

List<Students> studentList { get; set; }
String currentSort { get; set; }

public StudentWrapper() {

studentlist = new List<Students>();

}

在您的控制器中，您将创建一个新的StudentWrapper

StudentWrapper sw = new StudentWrapper();

并设置学生列表：

sw.studentList = db.Students.ToList();

和sortOrder

sw.currentSort = SortOder;

您将此模型传递给视图

return View(sw);

在您的视图中，您将使用StudentWrapper

@model List<MVCAppName.Models.StudentWrapper>

我不知道你的传呼是如何工作的，所以你必须弄清楚这一点。

但是我也没有看到使用ViewBag的任何问题。

如何使用ViewModel而不是ViewBag对实体列表进行排序？

3 个答案: