MVC Html.DropDownList 和DropDownListFor 的常用方法

一、非强类型：

第一种，还是级联

var ProductsSortList是数据库查询的List做成Json传给客户端，用jq处理<select>，但是Mvc不需要做更多的JQ工作，做成SelectListItem ，用@Html.DropDownList 和@DropDownListFor直接使用

1、JQ数据做的下拉框，基本就是传统的Select标签，借助EF强大的查询功能，客户端用jq处理ViewDATA

var ProductsSortList = OperateContext.Current.BLLSession.IProductsSortBLL.GetListBy_NoTrack(s => s.ProductsSortID > 0).Select(s => new Model.ViewModel.ProductsSort()            {                ProductsSortName = s.ProductsSortName,                ProductsSortID = s.ProductsSortID,                nodes = s.GoodsSorts.Select(t => new Model.ViewModel.GoodSort()                {                    GoodsSortID = t.GoodsSortId,                    GoodsSortName = t.GoodsSortName,                }).ToList()            }).ToList();            ViewData["ProductsSortDrop"] = Common.DataHelper.ToJSON(ProductsSortList);

<select name="ModifyProductsSort" id="ModifyProductsSort">    <option value="0" selected="selected">产品一级分类</option></select><select name="ModifyGoodSort" id="ModifyGoodSort">    <option value="0" selected="selected">产品二级分类</option></select>

3、JQ

<script type="text/javascript">    function escape2Html(str) {        var arrEntities = { 'lt': '<', 'gt': '>', 'nbsp': ' ', 'amp': '&', 'quot': '"' };        return str.replace(/&(lt|gt|nbsp|amp|quot);/ig, function (all, t) { return arrEntities[t]; });    }    //下拉框联动js    var a = '@ViewData["ProductsSortDrop"]';    j = escape2Html(a);        var obj = $.parseJSON(j);       $(document).ready(init);    function init() {        $.each(obj, function (index, val) {            $("<option value='" + val.ProductsSortID + "'>" + val.ProductsSortName + "</option>").appendTo($("#ModifyProductsSort"))//动态添加Option子项        });        $("select[name='ModifyProductsSort']").change(function () {            var selectedPortsSort = $(this).val();            if (selectedPortsSort == 0)            {                $("select[name='ModifyGoodSort']").innerHTML = "";                $("select[name='ModifyGoodSort']").html('<option value="产品二级分类" selected="selected">产品二级分类</option>');            }//清空二级下拉框            else {                document.getElementById("ModifyGoodSort").innerHTML = "";                ShowCityWithSelectedGoodSort(selectedPortsSort);            }        });    }    function ShowCityWithSelectedGoodSort(selectedPortsSort) {        $.each(obj, function (index, val) {            if (val.ProductsSortID == selectedPortsSort)            {                $.each(val.nodes, function (i, v)                {                    $("<option value='" + v.GoodsSortID + "'>" + v.GoodsSortName + "</option>").appendTo($("select[name='ModifyGoodSort']"))                })            }         });       }</script>

第二种，纯种MVC

Controller:var ProductsSortList是数据库查询的下拉框绑定做成SelectListItem 

var ProductsSortList = OperateContext.Current.BLLSession.IProductsSortBLL.GetListBy_NoTrack(s => s.ProductsSortID > 0).Select(s => new SelectListItem()            {                Text = s.ProductsSortName,                Value = s.ProductsSortID.ToString()            });            ViewData["ProductsSortDrop"] = ProductsSortList;

view:

@Html.DropDownList("ProductsSortDrop")

@Html.DropDownList("ProductsSortDrop")

还可以给其加上一个默认选项：@Html.DropDownList("ProductsSortDrop", "请选择");

二、强类型+非强类型(ViewData,并实现级联：

控制器：提供下拉框数据绑定

一个是产品一级目录ProdectsSortList得到，并在强类型中关联m => m.ProductsSortID,m => m.GoodsSortID

  var ProductsSortList = OperateContext.Current.BLLSession.IProductsSortBLL.GetListBy_NoTrack(s => s.ProductsSortID > 0).Select(s => new SelectListItem()            {                Text = s.ProductsSortName,                Value = s.ProductsSortID.ToString()            });            ViewData["ProductsSortDrop"] = ProductsSortList;            var GoodsSortDropList = OperateContext.Current.BLLSession.IGoodsSortBLL.GetListBy_NoTrack(s=>s.ProductsSortID==GoodsList.ProductsSortID).Select(s => new SelectListItem()                       {                           Text= s.GoodsSortName,                           Value = s.GoodsSortId.ToString()                       });            ViewData["GoodsSortDrop"] = GoodsSortDropList;

view:

绑定数据来自控制器的ViewData

@Html.DropDownListFor(m => m.ProductsSortID, ViewData["ProductsSortDrop"] as IEnumerable<SelectListItem>)

 @Html.DropDownListFor(m => m.GoodsSortID, ViewData["GoodsSortDrop"] as IEnumerable<SelectListItem>)

这样Mvc提交，自动的提交两个DropDownList的ID及value值

jq级联：

<script type="text/javascript">    $(document).ready(init);    function init() {        $("select[name='ProductsSortID']").change(function () {            document.getElementById("GoodsSortID").innerHTML = "";            var selectedProvince = $(this).val();            ShowCityWithSelectedProvince(selectedProvince);        });    }    function ShowCityWithSelectedProvince(province) {                $.ajax({            url: "@Url.Action("GoodsSortDrp", "AdminConsole")",            data: { ProductsSortId: province },            success: function (data) {                                console.log(data);                $.each(data, function (i, v) {                                        $("<option value='" + v.Value + "'>" + v.Text + "</option>").appendTo($("select[name='GoodsSortID']"))                })            }        });    }    </script>

三、强类型：
DropDownListFor常用的是两个参数的重载，第一参数是生成的select的名称，第二个参数是数据，用于将绑定数据源至DropDownListFor
Modle:
   public class SettingsViewModel
   {
       Repository rp =new Repository();
       public string ListName { get; set; }  
       public  IEnumerable<SelectListItem> GetSelectList()
       {
               var selectList = rp.GetArea().Select(a => new SelectListItem { 
                               Text=a.AreaName,
                               Value=a.AreaId.ToString()
                               });
               return selectList;
           }
       } 
Controller:
       public ActionResult Index()
       {
           return View(new SettingsViewModel());
       }
View:
@model Mvc３Applicationtest2.Models.SettingsViewModel
@Html.DropDownListFor(m=>m.ListName,Model.GetSelectList(),"请选择")