MVC3 Razor 下拉列表用于枚举

试着把我的项目升级到 MVC3，有些东西我就是找不到:

我有一个简单的数据类型 ENUMS:

public enum States()
{
AL,AK,AZ,...WY
}

在包含这个数据类型的模型视图中，我想用它作为 DropDown/SelectList:

public class FormModel()
{
public States State {get; set;}
}

很简单: 当我为这个分部类使用自动生成视图时，它忽略了这个类型。

我需要一个简单的选择列表，当我点击提交并通过我的 AJAX-JSON POST 方法进行处理时，将枚举的值设置为所选项。

而且比观点(? ? ? !) :

    <div class="editor-field">
@Html.DropDownListFor(model => model.State, model => model.States)
</div>

提前谢谢你的建议！

85135 次浏览
小开
最佳答案

I've just made one for my own project. The code below is part of my helper class, I hope that I got all methods needed. Write a comment if it doesn't work, and I'll check again.

public static class SelectExtensions
{


public static string GetInputName<TModel, TProperty>(Expression<Func<TModel, TProperty>> expression)
{
if (expression.Body.NodeType == ExpressionType.Call)
{
MethodCallExpression methodCallExpression = (MethodCallExpression)expression.Body;
string name = GetInputName(methodCallExpression);
return name.Substring(expression.Parameters[0].Name.Length + 1);


}
return expression.Body.ToString().Substring(expression.Parameters[0].Name.Length + 1);
}


private static string GetInputName(MethodCallExpression expression)
{
// p => p.Foo.Bar().Baz.ToString() => p.Foo OR throw...
MethodCallExpression methodCallExpression = expression.Object as MethodCallExpression;
if (methodCallExpression != null)
{
return GetInputName(methodCallExpression);
}
return expression.Object.ToString();
}


public static MvcHtmlString EnumDropDownListFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression) where TModel : class
{
string inputName = GetInputName(expression);
var value = htmlHelper.ViewData.Model == null
? default(TProperty)
: expression.Compile()(htmlHelper.ViewData.Model);


return htmlHelper.DropDownList(inputName, ToSelectList(typeof(TProperty), value.ToString()));
}


public static SelectList ToSelectList(Type enumType, string selectedItem)
{
List<SelectListItem> items = new List<SelectListItem>();
foreach (var item in Enum.GetValues(enumType))
{
FieldInfo fi = enumType.GetField(item.ToString());
var attribute = fi.GetCustomAttributes(typeof(DescriptionAttribute), true).FirstOrDefault();
var title = attribute == null ? item.ToString() : ((DescriptionAttribute)attribute).Description;
var listItem = new SelectListItem
{
Value = ((int)item).ToString(),
Text = title,
Selected = selectedItem == ((int)item).ToString()
};
items.Add(listItem);
}


return new SelectList(items, "Value", "Text", selectedItem);
}
}

Use it as:

Html.EnumDropDownListFor(m => m.YourEnum);

Update

I've created alternative Html Helpers. All you need to do to use them is to change your baseviewpage in views\web.config.

With them you can just do:

@Html2.DropDownFor(m => m.YourEnum);
@Html2.CheckboxesFor(m => m.YourEnum);
@Html2.RadioButtonsFor(m => m.YourEnum);

More info here: http://blog.gauffin.org/2011/10/first-draft-of-my-alternative-html-helpers/

小开

This would be helpful for selecting an int value from enum: Here SpecType is an int field... and enmSpecType is an enum.

@Html.DropDownList(
"SpecType",
YourNameSpace.SelectExtensions.ToSelectList(typeof(NREticaret.Core.Enums.enmSpecType),
Model.SpecType.ToString()), "Tip Seçiniz", new
{
gtbfieldid = "33",
@class = "small"
})
小开

I made the following change to the SelectList method to make it work a little better for me. Maybe it will be useful for others.

public static SelectList ToSelectList<T>(T selectedItem)
{
if (!typeof(T).IsEnum) throw new InvalidEnumArgumentException("The specified type is not an enum");


var selectedItemName = Enum.GetName(typeof (T), selectedItem);
var items = new List<SelectListItem>();
foreach (var item in Enum.GetValues(typeof(T)))
{
var fi = typeof(T).GetField(item.ToString());
var attribute = fi.GetCustomAttributes(typeof(DescriptionAttribute), true).FirstOrDefault();


var enumName = Enum.GetName(typeof (T), item);
var title = attribute == null ? enumName : ((DescriptionAttribute)attribute).Description;


var listItem = new SelectListItem
{
Value = enumName,
Text = title,
Selected = selectedItemName == enumName
};
items.Add(listItem);
}


return new SelectList(items, "Value", "Text");
}
小开

If you want something really simple then there's another way, depending on how you store the state in the database.

If you had an entity like this:

public class Address
{
//other address fields


//this is what the state gets stored as in the db
public byte StateCode { get; set; }


//this maps our db field to an enum
public States State
{
get
{
return (States)StateCode;
}
set
{
StateCode = (byte)value;
}
}
}

Then generating the dropdown would be as easy as this:

@Html.DropDownListFor(x => x.StateCode,
from State state in Enum.GetValues(typeof(States))
select new SelectListItem() { Text = state.ToString(), Value = ((int)state).ToString() }
);

Isn't LINQ pretty?

小开

I found a way simpler solution for this here: http://coding-in.net/asp-net-mvc-3-method-extension/

using System;
using System.Linq.Expressions;
using System.Web;
using System.Web.Mvc;
using System.Web.Mvc.Html;


namespace EnumHtmlHelper.Helper
{
public static class EnumDropDownList
{
public static HtmlString EnumDropDownListFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> modelExpression, string firstElement)
{
var typeOfProperty = modelExpression.ReturnType;
if(!typeOfProperty.IsEnum)
throw new ArgumentException(string.Format("Type {0} is not an enum", typeOfProperty));
var enumValues = new SelectList(Enum.GetValues(typeOfProperty));
return htmlHelper.DropDownListFor(modelExpression, enumValues, firstElement);
}   }   }

One line in razor will do it:

@Html.DropDownListFor(model => model.State, new SelectList(Enum.GetValues(typeof(MyNamespace.Enums.States))))

You can also find code for doing it with an extension method in the linked article.

小开 
    public enum EnumStates
{
AL = 0,
AK = 1,
AZ = 2,
WY = 3
}




@Html.DropDownListFor(model => model.State, (from EnumStates e in Enum.GetValues(typeof(EnumStates))
select new SelectListItem { Value = ((int)e).ToString(), Text = e.ToString() }), "select", new { @style = "" })
@Html.ValidationMessageFor(model => model.State)  //With select






//Or




@Html.DropDownListFor(model => model.State, (from EnumStates e in Enum.GetValues(typeof(EnumStates))
select new SelectListItem { Value = ((int)e).ToString(), Text = e.ToString() }), null, new { @style = "" })
@Html.ValidationMessageFor(model => model.State)   //With out select
小开

Based on the accepted answer by @jgauffin, I've created my own version of EnumDropDownListFor, which deals with the problem of selecting items.

The problem is detailed in another SO answer here:, and is basically down to a misunderstanding of the behaviour of the different overloads of DropDownList.

My full code (which includes overloads for htmlAttributes etc is:

public static class EnumDropDownListForHelper
{


public static MvcHtmlString EnumDropDownListFor<TModel, TProperty>(
this HtmlHelper<TModel> htmlHelper,
Expression<Func<TModel, TProperty>> expression
) where TModel : class
{
return EnumDropDownListFor<TModel, TProperty>(
htmlHelper, expression, null, null);
}


public static MvcHtmlString EnumDropDownListFor<TModel, TProperty>(
this HtmlHelper<TModel> htmlHelper,
Expression<Func<TModel, TProperty>> expression,
object htmlAttributes
) where TModel : class
{
return EnumDropDownListFor<TModel, TProperty>(
htmlHelper, expression, null, htmlAttributes);
}


public static MvcHtmlString EnumDropDownListFor<TModel, TProperty>(
this HtmlHelper<TModel> htmlHelper,
Expression<Func<TModel, TProperty>> expression,
IDictionary<string, object> htmlAttributes
) where TModel : class
{
return EnumDropDownListFor<TModel, TProperty>(
htmlHelper, expression, null, htmlAttributes);
}


public static MvcHtmlString EnumDropDownListFor<TModel, TProperty>(
this HtmlHelper<TModel> htmlHelper,
Expression<Func<TModel, TProperty>> expression,
string optionLabel
) where TModel : class
{
return EnumDropDownListFor<TModel, TProperty>(
htmlHelper, expression, optionLabel, null);
}


public static MvcHtmlString EnumDropDownListFor<TModel, TProperty>(
this HtmlHelper<TModel> htmlHelper,
Expression<Func<TModel, TProperty>> expression,
string optionLabel,
IDictionary<string,object> htmlAttributes
) where TModel : class
{
string inputName = GetInputName(expression);
return htmlHelper.DropDownList(
inputName, ToSelectList(typeof(TProperty)),
optionLabel, htmlAttributes);
}


public static MvcHtmlString EnumDropDownListFor<TModel, TProperty>(
this HtmlHelper<TModel> htmlHelper,
Expression<Func<TModel, TProperty>> expression,
string optionLabel,
object htmlAttributes
) where TModel : class
{
string inputName = GetInputName(expression);
return htmlHelper.DropDownList(
inputName, ToSelectList(typeof(TProperty)),
optionLabel, htmlAttributes);
}




private static string GetInputName<TModel, TProperty>(
Expression<Func<TModel, TProperty>> expression)
{
if (expression.Body.NodeType == ExpressionType.Call)
{
MethodCallExpression methodCallExpression
= (MethodCallExpression)expression.Body;
string name = GetInputName(methodCallExpression);
return name.Substring(expression.Parameters[0].Name.Length + 1);


}
return expression.Body.ToString()
.Substring(expression.Parameters[0].Name.Length + 1);
}


private static string GetInputName(MethodCallExpression expression)
{
// p => p.Foo.Bar().Baz.ToString() => p.Foo OR throw...
MethodCallExpression methodCallExpression
= expression.Object as MethodCallExpression;
if (methodCallExpression != null)
{
return GetInputName(methodCallExpression);
}
return expression.Object.ToString();
}




private static SelectList ToSelectList(Type enumType)
{
List<SelectListItem> items = new List<SelectListItem>();
foreach (var item in Enum.GetValues(enumType))
{
FieldInfo fi = enumType.GetField(item.ToString());
var attribute = fi.GetCustomAttributes(
typeof(DescriptionAttribute), true)
.FirstOrDefault();
var title = attribute == null ? item.ToString()
: ((DescriptionAttribute)attribute).Description;
var listItem = new SelectListItem
{
Value = item.ToString(),
Text = title,
};
items.Add(listItem);
}


return new SelectList(items, "Value", "Text");
}
}

I've written this up on my blog here.

小开

Same as Mike's (which is buried between lengthy responses)

model.truckimagelocation is class instance property of the TruckImageLocation enumeration type

@Html.DropDownListFor(model=>model.truckimagelocation,Enum.GetNames(typeof(TruckImageLocation)).ToArray().Select(f=> new SelectListItem() {Text = f, Value = f, Selected = false}))
小开

As of ASP.NET MVC 5.1 (RC1), EnumDropDownListFor is included by default as an extension method of HtmlHelper.

小开

you can use enum in your model

your Enum

public enum States()
{
AL,AK,AZ,...WY
}

make a model

public class enumclass
{
public States statesprop {get; set;}
}

in view 

@Html.Dropdownlistfor(a=>a.statesprop)
小开

I was able to do this in a one liner.

@Html.DropDownListFor(m=>m.YourModelProperty,new SelectList(Enum.GetValues(typeof(YourEnumType))))
小开

The easiest answer in MVC5 is Define Enum:

public enum ReorderLevels {
zero = 0,
five = 5,
ten = 10,
fifteen = 15,
twenty = 20,
twenty_five = 25,
thirty = 30
}

Bind In View:

        <div class="form-group">
<label>Reorder Level</label>
@Html.EnumDropDownListFor(m => m.ReorderLevel, "Choose Me", new { @class = "form-control" })
</div>
小开

This is most generic code which will be used for all Enums.

public static class UtilitiesClass
{


public static SelectList GetEnumType(Type enumType)
{
var value = from e in Enum.GetNames(enumType)
select new
{
ID = Convert.ToInt32(Enum.Parse(enumType, e, true)),
Name = e
};
return new SelectList(value, "ID", "Name");
}
}

Action Method

ViewBag.Enum= UtilitiesClass.GetEnumType(typeof (YourEnumType));

View.cshtml

 @Html.DropDownList("Type", (IEnumerable<SelectListItem>)ViewBag.Enum, new { @class = "form-control"})

提交答案