下拉 onchange 加载另一个下拉 MVC4

Question

在我看来，我正在填充两个下拉列表（类别和子类别）。

我正在通过我的控制器执行此操作，并且我希望根据从 Category 中选择的项目来填充 SubCategory 的下拉列表。

任何建议如何做到这一点，是否有更好和更有效的方式来填充下拉列表？

Controller:

public ActionResult Edit(int id)
    {
        EntryViewModel model = (from subcat in dc.SubCategory
                                join en in dc.Entry on subcat.SubCategoryId equals en.SubCategoryId
                                join cat in dc.Category on subcat.CategoryId equals cat.Id
                                where en.Id == id
                                select new EntryViewModel {
                                    Id = en.Id,
                                    Title = en.Title,
                                    Username = en.Username,
                                    Password = en.Password,
                                    Url = en.Url,
                                    Description = en.Description,
                                    CategoryId = cat.Id,
                                    CategoryName = cat.Name,
                                    SubCategoryId = subcat.SubCategoryId,
                                    SubCategoryName = subcat.Name
                                }).First();

        string selectedCat = (from cat in dc.Category
                           join en in dc.SubCategory on cat.Id equals en.SubCategoryId
                           where cat.Id == en.SubCategoryId
                           select cat.Name).First();

        ViewBag.SubjectNameCat = new SelectList(dc.Category, "Id", "Name", selectedCat);

        string selected = (from cat in dc.SubCategory
                           join en in dc.Entry on cat.SubCategoryId equals en.SubCategoryId
                           where en.Id == id
                           select cat.Name).First();

        ViewBag.SubjectName = new SelectList(dc.SubCategory, "SubCategoryId", "Name", selected);

        return View(model);
    }

查看：为简单起见，仅显示下拉列表

<div class="editor-label">
        Category
    </div>
    <div class="editor-field">
        @Html.DropDownListFor(model => model.CategoryId, (IEnumerable<SelectListItem>)ViewBag.SubjectNameCat,
               new { @class = "form-control" })
    </div>

    <div class="editor-label">
        SubCategory
    </div>
    <div class="editor-field">
        @Html.DropDownListFor(model => model.SubCategoryId, (IEnumerable<SelectListItem>)ViewBag.SubjectName,
               new { @class = "form-control" })
    </div>

Answer 1

@PetarS 试试这个最适合我的很棒的插件。 https://github.com/rajkaimal/CascadingDropDown