Html.EnumDropdownListFor：显示一个默认的文本 [英] Html.EnumDropdownListFor: Showing a default text

问题描述

在我看来，我有一个 enumdropdownlist （ASP中的一项新功能.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"})

如果我执行上述code为我的下枚举的DropDownList。

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我的DropDownList有一个值（自定义文本）
而这也正是我试图

but by default I want my 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"})

但现在的问题是，当我运行它，我的DropDownList的是这样的

因此，默认的文本要显示默认情况下不会出现。
如果用户选择选择一个许可证，并试图提交表单，它只一个错误说选择许可证，但它并不显示为默认文本。
这是我需要改变？

but now the problem is when i run it, my dropdownlist looks like this So, the default text want to show doesn't appear by default. If 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?

诗：图像页面截图时加载。默认情况下它会告诉审判选定的选项。

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

尝试改变首页的 LicenseTypes 从 1 开始不 0 象下面这样：

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

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

然后你可以使用范围属性，确认所选的许可证类型如下图所示：

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，在你看来：

Finally, in your view:

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

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