演练5-2：Contoso大学校园管理2

一、添加列标题排序功能

      我们将增加Student/Index页面的功能，为列标题添加超链接，用户可以点击列标题对那一列进行排序。

1.修改Index方法

public ActionResult Index(string sortOrder)
{
   ViewBag.NameSortParm = String.IsNullOrEmpty(sortOrder) ? "Name_desc" : "";
   ViewBag.DateSortParm = sortOrder == "Date" ? "Date_desc" : "Date";
   var students = from s in db.Students
                  select s;
   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;
      default:
         students = students.OrderBy(s => s.LastName);
         break;
   }
   return View(students.ToList());
}

      第一次Index页面响应的时候，没有query string，学生按照LastName升序排序，这是?:表达式的默认值，switch 语句执行升序操作。当用户点击列标题的超链接，正确的sortOrder参数传给query string。

      两个ViewBag变量用来区分列标题的超链接，是选择哪一个query string。

2.在StudentIndex视图中，添加列标题超链接

<p>
    @Html.ActionLink("Create New", "Create")
</p>
<table>
    <tr>
        <th>
            @Html.ActionLink("Last Name", "Index", new { sortOrder = ViewBag.NameSortParm })
        </th>
        <th>First Name
        </th>
        <th>
            @Html.ActionLink("Enrollment Date", "Index", new { sortOrder = ViewBag.DateSortParm })
        </th>
        <th></th>
    </tr>

    @foreach (var item in Model)
    {

       运行验证效果。

二、添加一个搜索文本框

      添加一个按照first name、last name搜索的文本框，实现对数据的过滤。

1.Index方法中添加过滤功能

public ViewResult Index(string sortOrder, string searchString)
{
    ViewBag.NameSortParm = String.IsNullOrEmpty(sortOrder) ? "name_desc" : "";
    ViewBag.DateSortParm = sortOrder == "Date" ? "date_desc" : "Date";
    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;
        default:
            students = students.OrderBy(s => s.LastName);
            break;
    }

    return View(students.ToList());
}

2.在Index视图中添加Search文本框

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

@using (Html.BeginForm())
{
    <p>
        Find by name: @Html.TextBox("SearchString")  
        <input type="submit" value="Search" /></p>
}

<table>
    <tr>

      运行查看效果。

      细心的同学有没有发现神马问题？搜索和排序功能同时能用么？

 三、添加分页功能

      我们将使用PagedList.Mvc NuGet包，实现分页功能。

1.安装PagedList.MVC NuGet Package

      PagedList包安装了一个PagedList集合类型，并且扩展方法适用于IQueryable和IEnumerable集合。

2.为Index方法添加分页功能

using PagedList;

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";

   if (searchString != null)
   {
      page = 1;
   }
  else
   {
      searchString = currentFilter;
   }

   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;
      default:  // Name ascending 
         students = students.OrderBy(s => s.LastName);
         break;
   }

   int pageSize = 3;
   int pageNumber = (page ?? 1);
   return View(students.ToPagedList(pageNumber, pageSize));
}

 3.在StudentIndex视图，添加页码链接

@model PagedList.IPagedList<ContosoUniversity.Models.Student>
@using PagedList.Mvc; 
<link href="~/Content/PagedList.css" rel="stylesheet" type="text/css" />

@{
    ViewBag.Title = "Students";
}

<h2>Students</h2>

<p>
    @Html.ActionLink("Create New", "Create")
</p>
@using (Html.BeginForm("Index", "Student", FormMethod.Get))
{
    <p>
        Find by name: @Html.TextBox("SearchString", ViewBag.CurrentFilter as string)  
        <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>
        First Name
    </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.EnrollmentDate)
        </td>
    </tr>
}

</table>
<br />
Page @(Model.PageCount < Model.PageNumber ? 0 : Model.PageNumber) of @Model.PageCount

@Html.PagedListPager( Model, page => Url.Action("Index", new { page, sortOrder = ViewBag.CurrentSort, currentFilter=ViewBag.CurrentFilter }) )

      你可以使用PagedListPager帮助器定制自己的分页效果，包括URLs和样式，查看更多信息请点击TroyGoode  / PagedList on the GitHub site。

      @Html.TextBox("SearchString", ViewBag.CurrentFilter as string)  中，ViewBag的值绑定都SearchString文本框上。

四、创建学生数据分析页面

      在About页面中，我们将显示每天有多少学生注册。

1.创建视图模型

using System;
using System.ComponentModel.DataAnnotations;

namespace ContosoUniversity.ViewModels
{
    public class EnrollmentDateGroup
    {
        [DataType(DataType.Date)]
        public DateTime? EnrollmentDate { get; set; }

        public int StudentCount { get; set; }
    }
}

2.修改Home控制器

using ContosoUniversity.DAL;
using ContosoUniversity.ViewModels;

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

public ActionResult About()
{
    var data = from student in db.Students
               group student by student.EnrollmentDate into dateGroup
               select new EnrollmentDateGroup()
               {
                   EnrollmentDate = dateGroup.Key,
                   StudentCount = dateGroup.Count()
               };
    return View(data);
}

protected override void Dispose(bool disposing)
{
    db.Dispose();
    base.Dispose(disposing);
}

3.修改About视图

@model IEnumerable<ContosoUniversity.ViewModels.EnrollmentDateGroup>
           
@{
    ViewBag.Title = "Student Body Statistics";
}

<h2>Student Body Statistics</h2>

<table>
    <tr>
        <th>
            Enrollment Date
        </th>
        <th>
            Students
        </th>
    </tr>

@foreach (var item in Model) {
    <tr>
        <td>
            @Html.DisplayFor(modelItem => item.EnrollmentDate)
        </td>
        <td>
            @item.StudentCount
        </td>
    </tr>
}
</table>