c# - MVC5 如何从用户写入下拉值

Question

好的，我的下拉框开始工作了，我有我的选项，如果我选择任何一个，我想写下提交的所选项目的值，听起来很简单吧？好吧，每次我单击任何选项并提交时，该值都会显示在 URL 上，但我似乎无法将其写出来...

View (索引.cshtml):

<p>Dropdown Using viewbag with Html.DropDownList </p>
<br/>
<div>
        @using (Html.BeginForm("dropDown", "Home", FormMethod.Get))
    {
        @Html.DropDownList("ListItem")

        <button type="submit"></button>
    }

</div>

<p>@ViewBag.SelectedValue</p> //should print the value I selected but it does nothing...

Controller (HomeController.cs):

public ActionResult Index()
    {
        List<SelectListItem> ObjItem = new List<SelectListItem>()
        {
      new SelectListItem {Text="Select",Value="0",Selected=true },
      new SelectListItem {Text="ASP.NET",Value="1" },
      new SelectListItem {Text="C#",Value="2"},
      new SelectListItem {Text="MVC",Value="3"},
      new SelectListItem {Text="SQL",Value="4" },
        };
        ViewBag.ListItem = ObjItem;

        return View("Index");
    }

    public ActionResult dropDown(List<SelectListItem> ListItem)
    {
        ViewBag.SelectedValue = ListItem[0].Value; //crossing fingers this has the value I want to print


        return this.View("Index");
    } 

Answer 1

这样试试

View (索引.cshtml):

<div>
    @using (Html.BeginForm("dropDown", "Home", FormMethod.Post))
    {
        @Html.DropDownList("ListItem")

        <button type="submit">Submit</button>
    }

</div>

<p>@ViewBag.SelectedValue</p>

Controller (HomeController.cs):

        public ActionResult Index()
        {
            bindCombo();
            return View();
        }

        private void bindCombo()
        {
            List<SelectListItem> ObjItem = new List<SelectListItem>()
            {
                new SelectListItem {Text="Select",Value="Select",Selected=true },
                new SelectListItem {Text="ASP.NET",Value="ASP.NET" },
                new SelectListItem {Text="C#",Value="C#"},
                new SelectListItem {Text="MVC",Value="MVC"},
                new SelectListItem {Text="SQL",Value="SQL" },
            };
            ViewBag.ListItem = ObjItem;
        }

        [HttpPost]
        public ActionResult dropDown(string ListItem)
        {
            ViewBag.SelectedValue = ListItem;
            bindCombo();
            return View("index");
        }