我正在尝试使用Html。下拉列表扩展方法,但不知道如何与枚举一起使用它。
假设我有一个这样的枚举:
public enum ItemTypes
{
Movie = 1,
Game = 2,
Book = 3
}
我如何去创建一个下拉与这些值使用Html。下拉列表扩展方法?
或者我最好的办法是简单地创建一个for循环并手动创建Html元素?
我正在尝试使用Html。下拉列表扩展方法,但不知道如何与枚举一起使用它。
假设我有一个这样的枚举:
public enum ItemTypes
{
Movie = 1,
Game = 2,
Book = 3
}
我如何去创建一个下拉与这些值使用Html。下拉列表扩展方法?
或者我最好的办法是简单地创建一个for循环并手动创建Html元素?
当前回答
我想以一种不同的方式回答这个问题,用户不需要在控制器或Linq表达式中做任何事情。这种方式……
我有一个ENUM
public enum AccessLevelEnum
{
/// <summary>
/// The user cannot access
/// </summary>
[EnumMember, Description("No Access")]
NoAccess = 0x0,
/// <summary>
/// The user can read the entire record in question
/// </summary>
[EnumMember, Description("Read Only")]
ReadOnly = 0x01,
/// <summary>
/// The user can read or write
/// </summary>
[EnumMember, Description("Read / Modify")]
ReadModify = 0x02,
/// <summary>
/// User can create new records, modify and read existing ones
/// </summary>
[EnumMember, Description("Create / Read / Modify")]
CreateReadModify = 0x04,
/// <summary>
/// User can read, write, or delete
/// </summary>
[EnumMember, Description("Create / Read / Modify / Delete")]
CreateReadModifyDelete = 0x08,
/*/// <summary>
/// User can read, write, or delete
/// </summary>
[EnumMember, Description("Create / Read / Modify / Delete / Verify / Edit Capture Value")]
CreateReadModifyDeleteVerify = 0x16*/
}
现在我可以使用这个enum简单地创建一个下拉列表。
@Html.DropDownList("accessLevel",new SelectList(AccessLevelEnum.GetValues(typeof(AccessLevelEnum))),new { @class = "form-control" })
OR
@Html.DropDownListFor(m=>m.accessLevel,new SelectList(AccessLevelEnum.GetValues(typeof(AccessLevelEnum))),new { @class = "form-control" })
如果你想让一个索引被选中,那么试试这个
@Html.DropDownListFor(m=>m.accessLevel,new SelectList(AccessLevelEnum.GetValues(typeof(AccessLevelEnum)) , AccessLevelEnum.NoAccess ),new { @class = "form-control" })
这里我使用了AccessLevelEnum。NoAccess作为默认选择下拉菜单的额外参数。
其他回答
在ASP。NET MVC 5.1,他们添加了EnumDropDownListFor()助手,所以不需要自定义扩展:
模型:
public enum MyEnum
{
[Display(Name = "First Value - desc..")]
FirstValue,
[Display(Name = "Second Value - desc...")]
SecondValue
}
观点:
@Html.EnumDropDownListFor(model => model.MyEnum)
使用标签助手(ASP。Net MVC 6):
<select asp-for="@Model.SelectedValue" asp-items="Html.GetEnumSelectList<MyEnum>()">
谢谢你的解决方案,它可以完美地应用在我的情况。唯一的问题是我必须把它翻译成VB。但现在已经完成了,为了节省其他人的时间(以防他们需要),我把它放在这里:
Imports System.Runtime.CompilerServices
Imports System.ComponentModel
Imports System.Linq.Expressions
Public Module HtmlHelpers
Private Function GetNonNullableModelType(modelMetadata As ModelMetadata) As Type
Dim realModelType = modelMetadata.ModelType
Dim underlyingType = Nullable.GetUnderlyingType(realModelType)
If Not underlyingType Is Nothing Then
realModelType = underlyingType
End If
Return realModelType
End Function
Private ReadOnly SingleEmptyItem() As SelectListItem = {New SelectListItem() With {.Text = "", .Value = ""}}
Private Function GetEnumDescription(Of TEnum)(value As TEnum) As String
Dim fi = value.GetType().GetField(value.ToString())
Dim attributes = DirectCast(fi.GetCustomAttributes(GetType(DescriptionAttribute), False), DescriptionAttribute())
If Not attributes Is Nothing AndAlso attributes.Length > 0 Then
Return attributes(0).Description
Else
Return value.ToString()
End If
End Function
<Extension()>
Public Function EnumDropDownListFor(Of TModel, TEnum)(ByVal htmlHelper As HtmlHelper(Of TModel), expression As Expression(Of Func(Of TModel, TEnum))) As MvcHtmlString
Return EnumDropDownListFor(htmlHelper, expression, Nothing)
End Function
<Extension()>
Public Function EnumDropDownListFor(Of TModel, TEnum)(ByVal htmlHelper As HtmlHelper(Of TModel), expression As Expression(Of Func(Of TModel, TEnum)), htmlAttributes As Object) As MvcHtmlString
Dim metaData As ModelMetadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData)
Dim enumType As Type = GetNonNullableModelType(metaData)
Dim values As IEnumerable(Of TEnum) = [Enum].GetValues(enumType).Cast(Of TEnum)()
Dim items As IEnumerable(Of SelectListItem) = From value In values
Select New SelectListItem With
{
.Text = GetEnumDescription(value),
.Value = value.ToString(),
.Selected = value.Equals(metaData.Model)
}
' If the enum is nullable, add an 'empty' item to the collection
If metaData.IsNullableValueType Then
items = SingleEmptyItem.Concat(items)
End If
Return htmlHelper.DropDownListFor(expression, items, htmlAttributes)
End Function
End Module
你可以这样使用它:
@Html.EnumDropDownListFor(Function(model) (model.EnumField))
使用Prise的扩展方法来解决获取数字而不是文本的问题。
public static SelectList ToSelectList<TEnum>(this TEnum enumObj)
{
var values = from TEnum e in Enum.GetValues(typeof(TEnum))
select new { ID = (int)Enum.Parse(typeof(TEnum),e.ToString())
, Name = e.ToString() };
return new SelectList(values, "Id", "Name", enumObj);
}
这里是Martin Faartoft的变种,你可以放自定义标签,这对本地化很好。
public static class EnumHtmlHelper
{
public static SelectList ToSelectList<TEnum>(this TEnum enumObj, Dictionary<int, string> customLabels)
where TEnum : struct, IComparable, IFormattable, IConvertible
{
var values = from TEnum e in Enum.GetValues(typeof(TEnum))
select new { Id = e, Name = customLabels.First(x => x.Key == Convert.ToInt32(e)).Value.ToString() };
return new SelectList(values, "Id", "Name", enumObj);
}
}
视图中使用:
@Html.DropDownListFor(m => m.Category, Model.Category.ToSelectList(new Dictionary<int, string>() {
{ 1, ContactResStrings.FeedbackCategory },
{ 2, ContactResStrings.ComplainCategory },
{ 3, ContactResStrings.CommentCategory },
{ 4, ContactResStrings.OtherCategory }
}), new { @class = "form-control" })
@Html.ValidationMessageFor(m => m.Category)
好吧,我真的是姗姗姗迟了,但无论如何,我已经在博客上讨论了这个主题,在这个主题中我创建了一个EnumHelper类,它可以实现非常简单的转换。
http://jnye.co/Posts/4/creating-a-dropdown-list-from-an-enum-in-mvc-and-c%23
在你的控制器中:
//If you don't have an enum value use the type
ViewBag.DropDownList = EnumHelper.SelectListFor<MyEnum>();
//If you do have an enum value use the value (the value will be marked as selected)
ViewBag.DropDownList = EnumHelper.SelectListFor(MyEnum.MyEnumValue);
在您看来:
@Html.DropDownList("DropDownList")
@* OR *@
@Html.DropDownListFor(m => m.Property, ViewBag.DropDownList as SelectList, null)
helper类:
public static class EnumHelper
{
// Get the value of the description attribute if the
// enum has one, otherwise use the value.
public static string GetDescription<TEnum>(this TEnum value)
{
var fi = value.GetType().GetField(value.ToString());
if (fi != null)
{
var attributes = (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
if (attributes.Length > 0)
{
return attributes[0].Description;
}
}
return value.ToString();
}
/// <summary>
/// Build a select list for an enum
/// </summary>
public static SelectList SelectListFor<T>() where T : struct
{
Type t = typeof(T);
return !t.IsEnum ? null
: new SelectList(BuildSelectListItems(t), "Value", "Text");
}
/// <summary>
/// Build a select list for an enum with a particular value selected
/// </summary>
public static SelectList SelectListFor<T>(T selected) where T : struct
{
Type t = typeof(T);
return !t.IsEnum ? null
: new SelectList(BuildSelectListItems(t), "Text", "Value", selected.ToString());
}
private static IEnumerable<SelectListItem> BuildSelectListItems(Type t)
{
return Enum.GetValues(t)
.Cast<Enum>()
.Select(e => new SelectListItem { Value = e.ToString(), Text = e.GetDescription() });
}
}