在 asp.net mvc 中验证下拉列表 [英] validate a dropdownlist in asp.net mvc

问题描述

//在控制器中ViewBag.Categories = categoryRepository.GetAllCategories().ToList();//在视图中@Html.DropDownList("Cat", new SelectList(ViewBag.Categories,"ID", "CategoryName"))

我怎样才能让它默认显示-选择类别-"

并验证以检查选择了某些内容(客户端和模型上)

谢谢

解决方案

我简直不敢相信还有人在 ASP.NET MVC 3 中使用 ViewData/ViewBag 而不是强类型视图和视图模型:

>

公共类 MyViewModel{[必需的]公共字符串 CategoryId { 获取；放;}公共 IEnumerable类别 { 得到;放;}}

并在您的控制器中:

公共类 HomeController:控制器{公共 ActionResult 索引(){var 模型 = 新的 MyViewModel{Categories = Repository.GetCategories()}返回视图(模型)；}[HttpPost]公共 ActionResult 索引(MyViewModel 模型){如果 (!ModelState.IsValid){//有一个验证错误 =>//重新绑定类别并重新显示视图model.Categories = Repository.GetCategories();返回视图(模型)；}//在这个阶段模型正常 =>对选定的类别做一些事情return RedirectToAction("成功");}}

然后在您的强类型视图中:

@Html.DropDownListFor(x =>x.CategoryId,new SelectList(Model.Categories, "ID", "CategoryName"),-- 请选择一个类别--")@Html.ValidationMessageFor(x => x.CategoryId)

此外，如果您想要客户端验证，请不要忘记引用必要的脚本:

<script src="@Url.Content("~/Scripts/jquery.validate.js")" type="text/javascript"></script><script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.js")" type="text/javascript"></script>

//in controller
ViewBag.Categories = categoryRepository.GetAllCategories().ToList();

//in view
 @Html.DropDownList("Cat", new SelectList(ViewBag.Categories,"ID", "CategoryName"))

How can I make it so that by default it says "-Select Category-"

And validate to check something is selected (client and on the model)

Thanks

解决方案

I just can't believe that there are people still using ViewData/ViewBag in ASP.NET MVC 3 instead of having strongly typed views and view models:

public class MyViewModel
{
    [Required]
    public string CategoryId { get; set; }

    public IEnumerable<Category> Categories { get; set; }
}

and in your controller:

public class HomeController: Controller
{
    public ActionResult Index()
    {
        var model = new MyViewModel
        {
            Categories = Repository.GetCategories()
        }
        return View(model);
    }

    [HttpPost]
    public ActionResult Index(MyViewModel model)
    {
        if (!ModelState.IsValid)
        {
            // there was a validation error =>
            // rebind categories and redisplay view
            model.Categories = Repository.GetCategories();
            return View(model);
        }
        // At this stage the model is OK => do something with the selected category
        return RedirectToAction("Success");
    }
}

and then in your strongly typed view:

@Html.DropDownListFor(
    x => x.CategoryId, 
    new SelectList(Model.Categories, "ID", "CategoryName"), 
    "-- Please select a category --"
)
@Html.ValidationMessageFor(x => x.CategoryId)

Also if you want client side validation don't forget to reference the necessary scripts:

<script src="@Url.Content("~/Scripts/jquery.validate.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.js")" type="text/javascript"></script>

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