MVC实现多选下拉框

using System.Collections.Generic;
using System.Web.Mvc;

namespace MvcApplication1.Models
{
public class CarVm
{
public string[] SelectedCars { get; set; }
public IEnumerable<SelectListItem>  AllCars { get; set; }
}
}

using System.Collections.Generic;
using System.Linq;
using System.Web.Mvc;
using MvcApplication1.Models;

namespace MvcApplication1.Controllers
{
public class HomeController : Controller
{
public ActionResult Index()
{
CarVm carVm = new CarVm();
carVm.SelectedCars = new string[]{"1","2"};
carVm.AllCars = GetAllCars();
return View(carVm);
}

[HttpPost]
public ActionResult SaveCars(CarVm carVm)
{
if (ModelState.IsValid)
{
return View(carVm);
}
return RedirectToAction("Index", carVm);
}

private IEnumerable<SelectListItem> GetAllCars()
{
List<SelectListItem> allCars = new List<SelectListItem>();
allCars.Add(new SelectListItem() {Value = "1",Text = "奔驰"});
allCars.Add(new SelectListItem() { Value = "2", Text = "宝马" });
allCars.Add(new SelectListItem() { Value = "3", Text = "奇瑞" });
allCars.Add(new SelectListItem() { Value = "4", Text = "比亚迪" });
allCars.Add(new SelectListItem() { Value = "5", Text = "起亚" });
allCars.Add(new SelectListItem() { Value = "6", Text = "大众" });
allCars.Add(new SelectListItem() { Value = "7", Text = "斯柯达" });
allCars.Add(new SelectListItem() { Value = "8", Text = "丰田" });
allCars.Add(new SelectListItem() { Value = "9", Text = "本田" });

return allCars.AsEnumerable();
}
}
}

@model MvcApplication1.Models.CarVm

@{
ViewBag.Title = "Index";
Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Index</h2>
<link href="~/Content/chosen.css" rel="stylesheet" />

@using (Html.BeginForm("SaveCars", "Home", FormMethod.Post))
{
@Html.LabelFor(m => m.SelectedCars,"最多选择2个选项") <br/>
@Html.ListBoxFor(m => m.SelectedCars, Model.AllCars, new {@class="chosen", multiple="multiple", style="width:350px;"}) <br/>
<input type="submit" value="提交"/>
}

@section scripts
{
<script src="~/Scripts/chosen.jquery.min.js"></script>
<script type="text/javascript">
$(function() {
$('.chosen').chosen({
max_selected_options: 2
});

$(".chosen-deselect").chosen(
{
allow_single_deselect: true
});

$(".chosen").chosen().change();
$(".chosen").trigger('liszt:updated');
});
</script>
}