Question

我正在尝试将视图包传递给DropDownList但是无效。

下拉列表错误

视图

   <div class="form-group">
            @Html.LabelFor(model => model.BanhoTosaId, "BanhoTosaId", htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
               @Html.DropDownList("TransporteId", ViewBag.BanhoTosaId, htmlAttributes: new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.BanhoTosaId, "", new { @class = "text-danger" })
            </div>
        </div>

控制器

 // GET: AgendaBTs/Create
        public ActionResult Create(int id, int pet)
        {

            ViewBag.BanhoTosaId = new SelectList(db.BanhoTosas, "BanhoTosaId", "Tipo");
            ViewBag.ClienteId = new SelectList(db.Clientes, "ClienteId", "Nome", id);
            ViewBag.PetId = new SelectList(db.Pets, "PetId", "PetNome", pet);
            ViewBag.TransporteId = new SelectList(db.Transportes, "TransporteId", "Tipo");

            if (ViewBag.BanhoTosaId != null && ViewBag.SelectedValue != null)
            {
                BanhoTosa BT = db.BanhoTosas.Find(ViewBag.BanhoTosaId);
                Transporte TS = db.Transportes.Find(ViewBag.TransporteId);
                decimal valorSoma = BT.Valor + TS.Valor;
                ViewBag.Total = valorSoma;
            }
            else
            {
                ViewBag.Total = 0;
            }

            return View();
        }

如果我这样下拉@Html.DropDownList（“TransporteId”，null，htm .... 在控制器中if，你抛出了else方法。

我该怎么做才能解决这个问题？

Answer 1

你需要施放ViewBag.BanhoTosaId：

 @Html.DropDownList("TransporteId", (List<SelectList>) ViewBag.BanhoTosaId, htmlAttributes: new { @class = "form-control" })

或

在Create操作中，将其替换为：

ViewBag.TransporteId = new SelectList(db.Transportes, "TransporteId", "Tipo");

通过

ViewBag.TransporteId = db.Transportes;

然后在剃刀视图中添加：

@Html.DropDownList("TransporteId", new SelectList(ViewBag.TransporteId , "TransporteId", "Tipo"))

Answer 2

你首先需要从你希望填充列表的数据中列出一个列表：

List<Category> CatList = db.Categories.ToList();

然后使用ViewBag：

 ViewBag.CategoriesList = new SelectList(CatList, "CategoryID", "CategoryName");

之后你将会查看并写下：

     <div class="form-group" style="margin-left:85px">
                    <div class="col-md-10">
  @Html.DropDownListFor(model => model.CategoryID, ViewBag.CategoriesList as SelectList,
             "Select Category", new { @class = "form-control" })
                    @Html.ValidationMessageFor(model => model.CategoryID, "", new { @class = "text-danger" })
                  
                    </div>
                </div>

这个例子来自我之前的工作

Answer 3

替换

 @Html.DropDownList("TransporteId", ViewBag.BanhoTosaId, htmlAttributes: new { @class = "form-control" })

带

@Html.DropDownList("TransporteId", (IEnumerable<SelectListItem>)ViewBag.BanhoTosaId,null, new { @class = "form-control" })

将viewbag传递给@Dropdownlist

3 个答案: