使用(Html.ValidationMessage)对mvc中的下拉列表进行简单验证

Question

调节器

var productList = Enumerable.Range(1, 80).Select(
    x => new SelectListItem { Value = x.ToString(), Text = x.ToString() }
);
ViewData["products"] = new SelectList(productList.ToList(), "Value", "Text");

视图

<%: Html.DropDownList("products", ViewData["products"] as SelectList, "--select--")%>
<%: Html.ValidationMessage("products", "Please Select the Product from the List")%> 
//This doesnt works on (ModelState.IsValid) I know the dropdown list data is coming
//from the view data not model , thats why model doesnt validate the particular dropdown 
//list while it validates other fields which are linked to model,
//Just want to know, how can i validate the above dropdownlist 

Answer 1

您将ddl的名称和值绑定到products.那是错的.当然,这是您的代码最少的问题.更大更严重的问题是您使用ViewData而不是使用强类型视图和视图模型.

所以有两种可能性:

1. 糟糕的一个:在您的视图模型上有一个属性,您将绑定您的下拉值.

   [Required(ErrorMessage = "Please Select the Product from the List")]
   public string SelectedProduct { get; set; }
   

   然后使用此属性名称作为弱类型DropDownList帮助程序和ViewData第二个agrument的第一个参数:

   <%= Html.DropDownList( 
       "SelectedProduct", 
       ViewData["products"] as SelectList, 
       "--select--"
   ) %>
   <%= Html.ValidationMessage("SelectedProduct") %>
   

2. 正确的方法:当然是使用真实视图模型(我厌倦了重复它,只是谷歌,你会得到像我一样的gazillions答案,只是在这个主题的网站上).它看起来像这样:

   <%: Html.DropDownListFor( 
       x => x.SelectedProduct, 
       Model.Products, 
       "--select--"
   ) %>
   <%= Html.ValidationMessageFor(x => x.SelectedProduct) %>