C# 如何将枚举的值放入 SelectList
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How to get the values of an enum into a SelectList
提问by Lee D
Imagine I have an enumeration such as this (just as an example):
想象一下，我有一个这样的枚举（仅作为示例）：
public enum Direction{
Horizontal = 0,
Vertical = 1,
Diagonal = 2
}
How can I write a routine to get these values into a System.Web.Mvc.SelectList, given that the contents of the enumeration are subject to change in future? I want to get each enumerations name as the option text, and its value as the value text, like this:
考虑到枚举的内容将来可能会发生变化，我如何编写一个例程来将这些值放入 System.Web.Mvc.SelectList 中？我想将每个枚举名称作为选项文本，并将其值作为值文本，如下所示：
<select>
<option value="0">Horizontal</option>
<option value="1">Vertical</option>
<option value="2">Diagonal</option>
</select>
This is the best I can come up with so far:
这是迄今为止我能想到的最好的：
public static SelectList GetDirectionSelectList()
{
Array values = Enum.GetValues(typeof(Direction));
List<ListItem> items = new List<ListItem>(values.Length);
foreach (var i in values)
{
items.Add(new ListItem
{
Text = Enum.GetName(typeof(Direction), i),
Value = i.ToString()
});
}
return new SelectList(items);
}
However this always renders the option text as 'System.Web.Mvc.ListItem'. Debugging through this also shows me that Enum.GetValues() is returning 'Horizontal, Vertical' etc. instead of 0, 1 as I would've expected, which makes me wonder what the difference is between Enum.GetName() and Enum.GetValue().
然而，这总是将选项文本呈现为“System.Web.Mvc.ListItem”。通过这个调试也告诉我 Enum.GetValues() 正在返回 'Horizontal, Vertical' 等，而不是我所期望的 0, 1，这让我想知道 Enum.GetName() 和 Enum 之间有什么区别。获取值（）。
采纳答案by Andrew Hare
To get the value of an enum you need to cast the enum to its underlying type:
要获取枚举的值，您需要将枚举转换为其基础类型：
Value = ((int)i).ToString();
回答by Brandon
It's been awhile since I've had to do this, but I think this should work.
自从我不得不这样做已经有一段时间了，但我认为这应该有效。
var directions = from Direction d in Enum.GetValues(typeof(Direction))
select new { ID = (int)d, Name = d.ToString() };
return new SelectList(directions , "ID", "Name", someSelectedValue);
回答by Carl H?rberg
maybe not an exact answer to the question, but in CRUD scenarios i usually implements something like this:
也许不是这个问题的确切答案，但在 CRUD 场景中，我通常会实现如下内容：
private void PopulateViewdata4Selectlists(ImportJob job)
{
ViewData["Fetcher"] = from ImportFetcher d in Enum.GetValues(typeof(ImportFetcher))
select new SelectListItem
{
Value = ((int)d).ToString(),
Text = d.ToString(),
Selected = job.Fetcher == d
};
}
PopulateViewdata4Selectlistsis called before View("Create") and View("Edit"), then and in the View:
PopulateViewdata4Selectlists在 View("Create") 和 View("Edit") 之前调用，然后在 View 中调用：
<%= Html.DropDownList("Fetcher") %>
and that's all..
就这样..
回答by Dan
This is what I have just made and personally I think its sexy:
这是我刚刚做的，我个人认为它很性感：
public static IEnumerable<SelectListItem> GetEnumSelectList<T>()
{
return (Enum.GetValues(typeof(T)).Cast<T>().Select(
enu => new SelectListItem() { Text = enu.ToString(), Value = enu.ToString() })).ToList();
}
I am going to do some translation stuff eventually so the Value = enu.ToString() will do a call out to something somewhere.
我最终会做一些翻译的东西，所以 Value = enu.ToString() 会调用某个地方的东西。
回答by zkarolyi
Or:
或者：
foreach (string item in Enum.GetNames(typeof(MyEnum)))
{
myDropDownList.Items.Add(new ListItem(item, ((int)((MyEnum)Enum.Parse(typeof(MyEnum), item))).ToString()));
}
回答by J.Noel.K
I wanted to do something very similar to Dann's solution, but I needed the Value to be an int and the text to be the string representation of the Enum. This is what I came up with:
我想做一些与 Dann 的解决方案非常相似的事情，但我需要 Value 是一个 int 并且文本是 Enum 的字符串表示。这就是我想出的：
public static IEnumerable<SelectListItem> GetEnumSelectList<T>()
{
return (Enum.GetValues(typeof(T)).Cast<int>().Select(e => new SelectListItem() { Text = Enum.GetName(typeof(T), e), Value = e.ToString() })).ToList();
}
回答by Joao Leme
public static SelectList ToSelectList<TEnum>(this TEnum enumObj) where TEnum : struct
{
if (!typeof(TEnum).IsEnum) throw new ArgumentException("An Enumeration type is required.", "enumObj");
var values = from TEnum e in Enum.GetValues(typeof(TEnum)) select new { ID = (int)Enum.Parse(typeof(TEnum), e.ToString()), Name = e.ToString() };
//var values = from TEnum e in Enum.GetValues(typeof(TEnum)) select new { ID = e, Name = e.ToString() };
return new SelectList(values, "ID", "Name", enumObj);
}
public static SelectList ToSelectList<TEnum>(this TEnum enumObj, string selectedValue) where TEnum : struct
{
if (!typeof(TEnum).IsEnum) throw new ArgumentException("An Enumeration type is required.", "enumObj");
var values = from TEnum e in Enum.GetValues(typeof(TEnum)) select new { ID = (int)Enum.Parse(typeof(TEnum), e.ToString()), Name = e.ToString() };
//var values = from TEnum e in Enum.GetValues(typeof(TEnum)) select new { ID = e, Name = e.ToString() };
if (string.IsNullOrWhiteSpace(selectedValue))
{
return new SelectList(values, "ID", "Name", enumObj);
}
else
{
return new SelectList(values, "ID", "Name", selectedValue);
}
}
回答by Hamid
return
Enum
.GetNames(typeof(ReceptionNumberType))
.Where(i => (ReceptionNumberType)(Enum.Parse(typeof(ReceptionNumberType), i.ToString())) < ReceptionNumberType.MCI)
.Select(i => new
{
description = i,
value = (Enum.Parse(typeof(ReceptionNumberType), i.ToString()))
});
回答by Fred
There is a new feature in ASP.NET MVC 5.1 for this.
为此，ASP.NET MVC 5.1 中有一个新功能。
http://www.asp.net/mvc/overview/releases/mvc51-release-notes#Enum
http://www.asp.net/mvc/overview/releases/mvc51-release-notes#Enum
@Html.EnumDropDownListFor(model => model.Direction)
回答by Miroslav Holec
I have more classes and methods for various reasons:
由于各种原因，我有更多的类和方法：
Enum to collection of items
枚举到项目集合
public static class EnumHelper
{
public static List<ItemDto> EnumToCollection<T>()
{
return (Enum.GetValues(typeof(T)).Cast<int>().Select(
e => new ItemViewModel
{
IntKey = e,
Value = Enum.GetName(typeof(T), e)
})).ToList();
}
}
Creating selectlist in Controller
在控制器中创建选择列表
int selectedValue = 1; // resolved from anywhere
ViewBag.Currency = new SelectList(EnumHelper.EnumToCollection<Currency>(), "Key", "Value", selectedValue);
MyView.cshtml
我的视图.cshtml
@Html.DropDownListFor(x => x.Currency, null, htmlAttributes: new { @class = "form-control" })
