cshtml部分代码:

<div class="editor-label">
                    @Html.Label("房间类型: ")
                    @Html.DropDownList("TypeID", ViewBag.Types as IEnumerable<SelectListItem>, "--请选择--")                    
                    @Html.Label("房间号: ")
                    @Html.DropDownList("RoomID", ViewBag.Rooms as IEnumerable<SelectListItem>, "--请选择--")
                </div>


js代码：

<script type="text/javascript">// <![CDATA[
    $(document).ready(function () {
        $("#TypeID").change(function () {
            var url = "/Guest/GetRoomNumber/" + $("#TypeID").val() + "/"; //规则是控制器/方法/参数
            $.getJSON(url, function (data) {
                $('#RoomID').html('');
                $.each(data, function (i, item) {
                    $('#RoomID').append($("<option></option>").val(item.RoomID).html(item.Number));
                });
            });
        });
    });// ]]>
                    </script>

Controller的代码：
public class GuestController : Controller
    {
         HotelManageEntities db = new HotelManageEntities();
          public ActionResult Create()
        {
             ViewBag.Types = db.RoomType.ToList().Select(c => new SelectListItem { Value = c.TypeID.ToString(), Text = c.TypeName });
            ViewBag.Rooms = db.Room.ToList().Select(c => new SelectListItem { Value = c.RoomID.ToString(), Text = c.Number });
            }
            
            public JsonResult GetRoomNumber(int id)
        {
            HotelManageEntities context = new Models.HotelManageEntities();

            var RoomNumber = from a in context.Room where a.TypeID == id select a; 
            return Json(RoomNumber.ToList(), JsonRequestBehavior.AllowGet);
        }
    }