Html.EnumDropdownListFor：显示默认文本 [英] Html.EnumDropdownListFor: Showing a default text

问题描述

在我看来，我有一个枚举列表（Asp中的一个新功能.Net MVC 5.1）。

In my view I have a enumdropdownlist (a new feature in Asp.Net MVC 5.1).

@Html.EnumDropDownListFor(m => m.SelectedLicense,new { @class="form-control"})

如果我执行上面的代码，我得到下面的枚举的下拉列表。 p>

If I execute the above code I get dropdownlist for my following enum.

public enum LicenseTypes
{
    Trial = 0,
    Paid = 1
}

但默认情况下，我希望我的下拉列表有一个值（自定义文本）
，是我尝试的

but by default I want my dropdownlist to have a value(custom text) and this is what I tried

@Html.EnumDropDownListFor(m => m.SelectedLicense,"Select a license" ,new { @class="form-control"})

但现在问题是我运行它的时候，我的下拉列表看起来像这样

所以，我想显示的默认文本默认情况下不会显示。
如果用户选择选择许可证并尝试提交表单，则会显示选择许可证的错误，但不会显示为默认文本。
我需要改变什么？

but now the problem is when i run it, my dropdownlist looks like this So, the default text I want to show doesn't appear by default. If a user selects "select a license" and tries to submit the form, it does show an error saying "select a license" but it doesn't show as default text. Something i need to change?

Ps：图像是加载页面的截图。默认情况下会显示为试用选项。

Ps: The image is the screenshot of the page when it loads. By default it'll show Trial as selected option.

推荐答案

尝试更改索引 LicenseTypes 从 1开始不 0 如下所示：

Try to change the Index of LicenseTypes start from 1 not 0 like below:

public enum LicenseTypes
{
    Trial = 1,
    Paid = 2
}

然后你可以使用 Range属性验证所选许可证类型，如下所示：

Then you can use Range attribute to validate the selected license type like below:

public class YourViewModel
{
     //Other properties
     [Range(1,int.MaxValue,ErrorMessage = "Select a correct license")]
     public LicenseTypes LicenseTypes { get; set; }
}

最后，在您的看法中：

   @Html.EnumDropDownListFor(m => m.LicenseTypes,"Select a license",new { @class = "form-control"})
   @Html.ValidationMessageFor(m => m.LicenseTypes)

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