asp.net mvc 多字段排序

以下代码可实现多字段排序，通过点击列标题，实现排序。

控制器：

public ActionResult Index(string sortOrder)
{
ViewBag.FirstNameSortParam = string.IsNullOrEmpty(sortOrder) ? "FirstName_desc" : "";
ViewBag.LastNameSortParam = sortOrder == "LastName" ? "LastName_desc" : "LastName";
ViewBag.DateSortParam = sortOrder == "date" ? "date_desc" : "date";
var students = from s in db.Students
select s;

switch (sortOrder)
{
case "FirstName_desc":
students = students.OrderByDescending(s => s.FirstMidName);
break;
case "LastName":
students = students.OrderBy(s => s.LastName);
break;
case "LastName_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.FirstMidName);
break;
}

return View(students.ToList());
}

视图：

<table class="table table-hover table-striped">
<thead>
<tr>
<th>
@Html.ActionLink("名", "Index", new { sortOrder = ViewBag.LastNameSortParam })

</th>
<th>
@Html.ActionLink("姓", "Index", new { sortOrder =ViewBag.FirstNameSortParam  })

</th>
<th>
@Html.ActionLink("入学时间", "Index", new { sortOrder = ViewBag.DateSortPaarm })
</th>
<th></th>
</tr>
</thead>
<tbody>
@foreach (var item in Model)
{ ........................................................