Question

heloo伙伴我已经使用Viewbag对象从mvc中的数据库填充了dropdownlist现在我想指定它的默认值，就像Select Supplier这里是我的Controler代码..

 public ActionResult Create()
    {
        //IEnumerable<SelectListItem> SuppliersList = db.Suppliers.Select(c => new SelectListItem
        //{
        //    Value = c.Name,
        //    Text = c.Name

        //});            

        ViewBag.SupplierList = new SelectList(db.Suppliers, "Name", "Name");
        return PartialView("_Create");
    }

    // POST: /Frames/Create
    // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
    // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
    [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<ActionResult> Create([Bind(Include="FrameId,Name,FrameCode,FrameFor,Brand,Material,Color,FrameType,FrameShape,Bridge,LensWidth,FrameWidth,TempleLength,LensHeight,FrameWeight,Quantity,PurchaseRate,SaleRate,Supplier,Discription,Status,CreatedOn")] Frame frame)
    {

        if (ModelState.IsValid)
        {
            db.Frames.Add(frame);
            await db.SaveChangesAsync();
            return Json(new { success = true });
        }



        return PartialView("_Create", frame);
    }

和我的ViewCode

<div class="col-md-3">
                    @Html.LabelFor(model => model.Supplier)
                    @Html.DropDownList("Supplier", ViewBag.SupplierList as SelectList, new { @class = "form-control"})
                    @Html.ValidationMessageFor(model => model.Supplier)
                </div>

Answer 1

如果您使用ViewBag和DropDownList html辅助方法，则应在{{1}中设置所选项目的名称（您使用Name作为SelectLis t的值属性的正弦值）因为这是你在ViewBag.Supplier辅助方法的第一个参数使用的值。

DropDownList

如果您想显示默认的“请选择”选项以及下拉选项，您可以使用此var suppliers = db.Suppliers.ToList(); ViewBag.SupplierList = new SelectList(suppliers , "Name", "Name"); // Here i am setting the 2 item in suppliers as the selected item. // You can change it as needed ViewBag.Supplier = suppliers[1].Name; return PartialView("_Create");方法的重载。

DropDownList

所以你的代码将是

public static MvcHtmlString DropDownList(
    this HtmlHelper htmlHelper,
    string name,
    IEnumerable<SelectListItem> selectList,
    string optionLabel,
    object htmlAttributes
)

另一种解决方案是不使用viewbag并使用强类型视图模型并使用@Html.DropDownList("Supplier", ViewBag.SupplierList as SelectList, "Please select", new { @class = "form-control" })辅助方法。 Here是如何做到的一个例子。

Answer 2

只需实现optionLabel覆盖。

@Html.DropDownList("Supplier", 
                   ViewBag.SupplierList as SelectList, 
                   "Select Supplier", 
                   new { @class = "form-control" })

如何指定下拉列表的默认值我使用mvc中的Viewbag从数据库填充

2 个答案: