MVC-填充下拉列表取决于另一个选择

如何解决MVC-填充下拉列表取决于另一个选择

我有三个下拉列表，每个下拉列表取决于先前的选择（股票，类别，项目）。 Viewbag从控制器填充的每个下拉列表 控制器：

 ViewBag.stock_id = new SelectList(db.stocks,"stock_id","stock_name");
    ViewBag.cat_id = new SelectList(db.categories,"cat_id","cat_name");
    ViewBag.item_id = new SelectList(db.items,"item_id","item_name");

 

   [HttpGet]
    public ActionResult UpdateitemDrop1(int stock_id)
    {
        
        var fromDatabaseEF = new SelectList(db.categories.Where(x => x.stock_id == stock_id).ToList(),"cat_name");
        SelectList vb = fromDatabaseEF;
        return Json(vb,JsonRequestBehavior.AllowGet);
    }


    [HttpGet]
    public ActionResult UpdateitemDrop2(int cat_id)
    {
        SelectList data= new SelectList(db.items.Where(x => x.cat_id == cat_id).ToList(),"item_name");
        return Json(data,JsonRequestBehavior.AllowGet);

    }

视图：

 <div class="form-group">
            @Html.LabelFor(model => model.stock_id,htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownList("stock_id",null,htmlAttributes: new { @class = "form-control",@id = "stock_id" })
                @Html.ValidationMessageFor(model => model.employee_id,"",new { @class = "text-danger" })
            </div>
        </div>
        <div class="form-group">
            @Html.LabelFor(model => model.cat_id,htmlAttributes: new { @class = "control-label col-md-2"})
            <div class="col-md-10">
                @Html.DropDownList("cat_id",@id = "cat_id",disabled = "disabled" })
                @Html.ValidationMessageFor(model => model.employee_id,new { @class = "text-danger" })
            </div>
        </div>
        <div class="form-group">
            @Html.LabelFor(model => model.item_id,htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownList("item_id",@id = "item_id",disabled = "disabled" })
                @Html.ValidationMessageFor(model => model.item_id,new { @class = "text-danger" })
            </div>
        </div>

<script>      
$(function () {
    $('#stock_id').change(function () {
        var select = $('#cat_id');
        var stockV = $("#stock_id :selected").val();
        alert();
        $.ajax({
            url: '/additions/UpdateitemDrop1',type: "GET",dataType: "JSON",data: { stock_id: stockV },success: function (vb) {
                
                select.empty();
                $(vb).each(function () {
                    select.add($("<option></option>").val(vb.cat_id).html(vb.cat_name));
                });

            }
        });
    });

    $('#cat_id').change(function () {
        var catV = $("#cat_id :selected").val();
        $('#item_id').prop("disabled",false);
        alert();
        $.ajax({
            url: '/additions/UpdateitemDrop2',data: { item_id: catV },success: function () {
                $("#item_id").html("");
                $("#item_id").empty();
                $.each(data,function (i,items) {
                    $("#item_id").append(
                        $('<option></option>').val(items.item_id).html(items.item_name));
                });
            }
        });
    });
});
    </script>

但是当我从第一个下拉列表（stock_id）中选择选项时，它会在“ empty（）”函数处停止，并且不会填充第二个下拉列表 有什么帮助吗？

解决方法

这会有所帮助。

控制器-我从Index16开始。

string RemoveComments(string textWithComments)
{
    StringBuilder textWithoutComments = new StringBuilder();

    string[] split = text.Replace(" ",null).Split('\r','\n');
    foreach (string line in split)
        if (line.Length >= 2 && line[0] == '*' && line[1] == '*') continue;
        else textWithoutComments.Append(line + "\r\n");

    return textWithoutComments.ToString();
}

查看

public class Stock
{
    public string Id { get; set; } //value
    public string Name { get; set; } //text
}

public class Category
{
    public string Id { get; set; }
    public string Name { get; set; }
}

public class Item
{
    public string Id { get; set; }
    public string Name { get; set; }
}

public class ViewModel
{
    public IList<Stock> StockList { get; set; }
    public IList<Category> CategoryList { get; set; }
    public IList<Item> ItemList { get; set; }
    public string SelectedStock { get; set; }
    public string SelectedCategory { get; set; }
    public string SelectedItem { get; set; }

}
public class HomeController : Controller
{
    [HttpGet]
    public ActionResult UpdateitemDrop1(string stock_id)
    {
        List<Stock> stocks;
        List<Category> categories;
        List<Item> items;
        PopulateViewBags(out stocks,out categories,out items);

        var q = categories.Where(x => x.Id == stock_id).ToArray();
        return Json(q,JsonRequestBehavior.AllowGet);
    }


    [HttpGet]
    public ActionResult UpdateitemDrop2(string cat_id)
    {
        List<Stock> stocks;
        List<Category> categories;
        List<Item> items;
        PopulateViewBags(out stocks,out items);

        ViewBag.item_id = new SelectList(items.Where(x => x.Id == cat_id));
        return Json(ViewBag.item_id,JsonRequestBehavior.AllowGet);
    }

    public ActionResult Index16()
    {
        List<Stock> stocks;
        List<Category> categories;
        List<Item> items;
        PopulateViewBags(out stocks,out items);

        var viewModel = new ViewModel { CategoryList = categories,ItemList = items,StockList = stocks };

        return View(viewModel);
    }

    private void PopulateViewBags(out List<Stock> stocks,out List<Category> categories,out List<Item> items)
    {
        stocks = new List<Stock> {
            new Stock {  Id = "1",Name = "Stock1"},new Stock {  Id = "2",Name = "Stock2"},new Stock {  Id = "3",Name = "Stock3"}
        };
        categories = new List<Category> {
            new Category {  Id = "1",Name = "Category1"},new Category {  Id = "2",Name = "Category2"},new Category {  Id = "3",Name = "Category3"}
        };
        items = new List<Item> {
            new Item {  Id = "1",Name = "Item1"},new Item {  Id = "2",Name = "Item2"},new Item {  Id = "3",Name = "Item3"}
        };
        ViewBag.cat_id = new SelectList(categories,"Id","Name");
        ViewBag.item_id = new SelectList(items,"Name");
        ViewBag.stock_id = new SelectList(stocks,"Name");
    }