ASP.NET MVC：DropDownList的验证 [英] ASP.NET MVC: DropDownList validation

问题描述

注：以下仅仅是一个例子。

我是pretty新的ASP.NET MVC和我试图让我周围的下拉列表的验证是如何工作的负责人。我有以下属性我 ProfileViewModel 类：

  [DisplayName的（性别）]
公共BOOL？性别{搞定;组; }
 

空是为了表示未知，真正女性和假男性。在视图模型构造I

  AllGenders =新的List＆LT; SelectListItem＆GT;（2）
             {
                 新SelectListItem的{text =未知，值=空}，
                 新SelectListItem的{text =男，值=假}，
                 新SelectListItem的{text =女，值=真}
             };
 

首先，看来我有填充列表与LT时使用的字符串; SelectListItem＆GT; ，感觉有点怪怪的。这真的是它是如何做的？

其次，当我在列表中选择未知验证失败告诉我：

'空'的值不是有​​效的性别。

这是为什么？当我删除了空选项，并更改性别来一个简单的布尔，一切似乎都很好。

这是ASPX：

 ＆LT;％= Html.DropDownList（性别，Model.AllGenders）％GT;
 

（我不能让 DropDownListFor 正常工作，似乎很多人有同样的问题。）

任何帮助AP preciated！

解决方案

 新SelectListItem的{text =未知，值=空}，
 

应该是：

 新SelectListItem的{text =未知，值=}，
 

发布，将导致空的限制。

Note: The following is just an example.

I'm pretty new to ASP.NET MVC and I'm trying to get my head around how validation of dropdown lists work. I have the following property in my ProfileViewModel class:

[DisplayName("Gender")]
public bool? Gender { get; set; }

null is meant to mean "unknown", true female and false male. In the view model constructor I

AllGenders = new List<SelectListItem>(2)
             {
                 new SelectListItem {Text = "Unknown", Value = "null"},
                 new SelectListItem {Text = "Male", Value = "false"},
                 new SelectListItem {Text = "Female", Value = "true"}
             };

First of all, it seems that I have to use strings when populating a List<SelectListItem>, which feels kinda weird. Is this really how it's done?

Secondly, when I choose "Unknown" in the list the validation fails telling me:

The value 'null' is not valid for Gender.

Why is that? When I remove the "null" option and change Gender to a simple bool, everything seems fine.

This is the ASPX:

<%= Html.DropDownList("Gender", Model.AllGenders) %>

(I can't get DropDownListFor to work correctly and it seems that many others have the same problem.)

Any help appreciated!

解决方案

new SelectListItem {Text = "Unknown", Value = "null"},

should be:

new SelectListItem {Text = "Unknown", Value = ""},

Posting "" will result in null being bound.

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