[asp.net mvc 奇淫巧技] 03 - 枚举特性扩展解决枚举命名问题和支持HtmlHelper

一、需求

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Text;
using System.Web.Mvc;
using System.Web.Routing;

namespace Emrys.EnumTools
{

/// <summary>
/// 枚举帮助类
/// </summary>
public static class EnumTools
{

/// <summary>
/// 获取当前枚举值的描述
/// </summary>
/// <param name="value"></param>
/// <returns></returns>
public static string GetDescription(this Enum value)
{
int order;
return GetDescription(value, out order);
}

/// <summary>
/// 获取当前枚举值的描述和排序
/// </summary>
/// <param name="value"></param>
/// <param name="order"></param>
/// <returns></returns>
public static string GetDescription(this Enum value, out int order)
{
string description = string.Empty;

Type type = value.GetType();

// 获取枚举
FieldInfo fieldInfo = type.GetField(value.ToString());

// 获取枚举自定义的特性DescriptionAttribute
object[] attrs = fieldInfo.GetCustomAttributes(typeof(DescriptionAttribute), false);
DescriptionAttribute attr = (DescriptionAttribute)attrs.FirstOrDefault(a => a is DescriptionAttribute);

order = 0;
description = fieldInfo.Name;

if (attr != null)
{
order = attr.Order;
description = attr.Name;
}
return description;

}

/// <summary>
/// 获取当前枚举的所有描述
/// </summary>
/// <param name="value"></param>
/// <returns></returns>
public static List<KeyValuePair<int, string>> GetAll<T>()
{
return GetAll(typeof(T));
}

/// <summary>
/// 获取所有的枚举描述和值
/// </summary>
/// <param name="type"></param>
/// <returns></returns>
public static List<KeyValuePair<int, string>> GetAll(Type type)
{

List<EnumToolsModel> list = new List<EnumToolsModel>();

// 循环枚举获取所有的Fields
foreach (var field in type.GetFields())
{
// 如果是枚举类型
if (field.FieldType.IsEnum)
{
object tmp = field.GetValue(null);
Enum enumValue = (Enum)tmp;
int intValue = Convert.ToInt32(enumValue);
int order;
string showName = enumValue.GetDescription(out order); // 获取描述和排序
list.Add(new EnumToolsModel { Key = intValue, Name = showName, Order = order });
}
}

// 排序并转成KeyValue返回
return list.OrderBy(i => i.Order).Select(i => new KeyValuePair<int, string>(i.Key, i.Name)).ToList();

}

/// <summary>
/// 枚举下拉
/// </summary>
/// <typeparam name="T">枚举类型</typeparam>
/// <param name="html"></param>
/// <param name="htmlAttributes"></param>
/// <returns></returns>
public static MvcHtmlString EnumToolsSelect<T>(this HtmlHelper html, object htmlAttributes = null)
{
return html.EnumToolsSelect(typeof(T), int.MaxValue, htmlAttributes);
}

/// <summary>
/// 枚举下拉
/// </summary>
/// <typeparam name="T">枚举类型</typeparam>
/// <param name="html"></param>
/// <param name="selectedValue">选择项</param>
/// <param name="htmlAttributes"></param>
/// <returns></returns>
public static MvcHtmlString EnumToolsSelect<T>(this HtmlHelper html, int selectedValue, object htmlAttributes = null)
{
return html.EnumToolsSelect(typeof(T), selectedValue, htmlAttributes);
}

/// <summary>
/// 枚举下拉
/// </summary>
/// <typeparam name="T">枚举类型</typeparam>
/// <param name="html"></param>
/// <param name="selectedValue">选择项</param>
/// <param name="htmlAttributes"></param>
/// <returns></returns>
public static MvcHtmlString EnumToolsSelect<T>(this HtmlHelper html, T selectedValue, object htmlAttributes = null)
{
return html.EnumToolsSelect(typeof(T), Convert.ToInt32(selectedValue), htmlAttributes);
}

/// <summary>
/// 枚举下拉
/// </summary>
/// <param name="html"></param>
/// <param name="enumType">枚举类型</param>
/// <param name="selectedValue">选择项</param>
/// <param name="htmlAttributes"></param>
/// <returns></returns>
public static MvcHtmlString EnumToolsSelect(this HtmlHelper html, Type enumType, int selectedValue, object htmlAttributes = null)
{
// 创建标签
TagBuilder tag = new TagBuilder("select");

// 添加自定义标签
if (htmlAttributes != null)
{
RouteValueDictionary htmlAttr = htmlAttributes as RouteValueDictionary ?? HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes);
tag.MergeAttributes(htmlAttr);
}
// 创建option集合
StringBuilder options = new StringBuilder();
foreach (var item in GetAll(enumType))
{
// 创建option
TagBuilder option = new TagBuilder("option");

// 添加值
option.MergeAttribute("value", item.Key.ToString());

// 设置选择项
if (item.Key == selectedValue)
{
option.MergeAttribute("selected", "selected");
}

// 设置option
option.SetInnerText(item.Value);
options.Append(option.ToString());
}
tag.InnerHtml = options.ToString();

// 返回MVCHtmlString
return MvcHtmlString.Create(tag.ToString());

}
/// <summary>
/// 下拉枚举
/// </summary>
/// <typeparam name="TModel">Model</typeparam>
/// <typeparam name="TProperty">属性</typeparam>
/// <param name="htmlHelper"></param>
/// <param name="expression"></param>
/// <param name="htmlAttributes"></param>
/// <returns></returns>
public static MvcHtmlString EnumToolsSelectFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, object htmlAttributes = null)
{
// 获取元数据meta
ModelMetadata modelMetadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);

Type enumType = modelMetadata.ModelType;

// 设置id name的属性值
var rvd = new RouteValueDictionary
{
{ "id", modelMetadata.PropertyName },
{ "name", modelMetadata.PropertyName }
};

// 添加自定义属性
if (htmlAttributes != null)
{
RouteValueDictionary htmlAttr = htmlAttributes as RouteValueDictionary ?? HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes);
foreach (var item in htmlAttr)
{
rvd.Add(item.Key, item.Value);
}
}

// 获取验证信息
IDictionary<string, object> validationAttributes = htmlHelper.GetUnobtrusiveValidationAttributes(modelMetadata.PropertyName, modelMetadata);

// 添加至自定义属性
if (validationAttributes != null)
{
foreach (var item in validationAttributes)
{
rvd.Add(item.Key, item.Value);
}
}
return htmlHelper.EnumToolsSelect(enumType, Convert.ToInt32(modelMetadata.Model), rvd);
}
}

/// <summary>
/// 枚举特性
/// </summary>
[AttributeUsage(AttributeTargets.Field, AllowMultiple = false, Inherited = false)]
public class DescriptionAttribute : Attribute
{
/// <summary>
/// 排序
/// </summary>
public int Order { get; set; }

/// <summary>
/// 名称
/// </summary>
public string Name { get; set; }

/// <summary>
/// 显示自定义描述名称
/// </summary>
/// <param name="name">名称</param>
public DescriptionAttribute(string name)
{
Name = name;
}

/// <summary>
/// 显示自定义名称
/// </summary>
/// <param name="name">名称</param>
/// <param name="order">排序</param>
public DescriptionAttribute(string name, int order)
{
Name = name;
Order = order;
}

}

/// <summary>
/// 枚举Model
/// </summary>
partial class EnumToolsModel
{
public int Order { get; set; }
public string Name { get; set; }
public int Key { get; set; }
}
}

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