使用下拉列表綁定枚舉並在MVC C＃中的get動作中設置選定值

Question

我有一個叫做CityType的Enum

public enum CityType
    {
        [Description("Select City")]
        Select = 0,

        [Description("A")]
        NewDelhi = 1,

        [Description("B")]
        Mumbai = 2,

        [Description("C")]
        Bangalore = 3,

        [Description("D")]
        Buxar = 4,

        [Description("E")]
        Jabalpur = 5
    }

從枚舉生成列表

IList<SelectListItem> list = Enum.GetValues(typeof(CityType)).Cast<CityType>().Select(x =>    new SelectListItem(){ 
    Text = EnumHelper.GetDescription(x), 
    Value = ((int)x).ToString()
}).ToList(); 

int city=0; 
if (userModel.HomeCity != null) city= (int)userModel.HomeCity;
ViewData["HomeCity"] = new SelectList(list, "Value", "Text", city);

綁定.cshtml

@Html.DropDownList("HomeCity",null,new { @style = "width:155px;", @class = "form-control" })

EnumHelper GetDescription類獲取Enum的描述

Answer 1

我在博客上寫了這個主題，我創建了一個EnumHelper來幫助完成這項常見任務。

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);

在您的視圖中：

@Html.DropDownList("DropDownList")
@* OR *@
@Html.DropDownListFor(m => m.Property, ViewBag.DropDownList as SelectList, null)

助手類：

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() });
    }
}

Answer 2

這是我在下拉列表中用於枚舉的代碼。 然后只需使用@ Html.DropDown / For（）; 並將此SelectList作為參數放入。

public static SelectList ToSelectList(this Type enumType, string selectedValue)
    {
        var items = new List<SelectListItem>();
        var selectedValueId = 0;
        foreach (var item in Enum.GetValues(enumType))
        {
            FieldInfo fi = enumType.GetField(item.ToString());
            DescriptionAttribute[] attributes = (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
            var title = "";
            if (attributes != null && attributes.Length > 0)
            {
                title = attributes[0].Description;
            }
            else
            {
                title = item.ToString();
            }

            var listItem = new SelectListItem
            {
                Value = ((int)item).ToString(),
                Text = title,
                Selected = selectedValue == ((int)item).ToString(),
            };
            items.Add(listItem);
        }

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

你也可以這樣擴展DropDownFor：

public static MvcHtmlString EnumDropdownListFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, Type enumType, object htmlAttributes = null)
    {
        ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);

        SelectList selectList = enumType.ToSelectList(metadata.Model.ToString());

        return htmlHelper.DropDownListFor(expression, selectList, htmlAttributes);
    }

用法然后如下所示：

@Html.EnumDropdownListFor(model => model.Property, typeof(SpecificEnum))