asp.net mvc dropdownlist 实现 aotopost 自动回发

public ActionResult Index(int? id)
{
IList<SelectListItem> item = new List<SelectListItem>();
int dllId = id ?? 0;
for (int i = 0; i < 50; i++)
{
SelectListItem sl = new SelectListItem();
sl.Text = (i + 10).ToString();
sl.Value = i.ToString();
if (i == id)
{
sl.Selected = true;
}
item.Add(sl);
}
ViewData["sl"] = item;
return View("test", "~/Views/Shared/Site.Master");
}

public ActionResult test()
{
string id = Request.Form["sl"].ToString();
return RedirectToAction("index", "test", new System.Web.Routing.RouteValueDictionary { {"id",id}});
}

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage" %>

<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
test
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

<h2>test</h2>
<select id="sel">
<option value="1">测试1</option>
</select>
<%= Html.ActionLink("s","index","test") %>
<% using (Html.BeginForm("test", "test", FormMethod.Post))
{ %>
<%= Html.DropDownList("sl")%>
<input type="submit" value="提交" />
<%} %>
<mce:script type="text/javascript"><!--
$("#sl").change(function() {
$(this).parents('form').submit();

});

// --></mce:script>
</asp:Content>