我有以下列举:
public enum AuthenticationMethod
{
FORMS = 1,
WINDOWSAUTHENTICATION = 2,
SINGLESIGNON = 3
}
然而问题是，当我请求AuthenticationMethod时，我需要“FORMS”这个词。表单而不是id
对于这个问题，我找到了以下解决方案(链接):
首先，我需要创建一个自定义属性“StringValue”:
public class StringValue : System.Attribute
{
private readonly string _value;
public StringValue(string value)
{
_value = value;
}
public string Value
{
get { return _value; }
}
}
然后我可以将这个属性添加到我的枚举器中:
public enum AuthenticationMethod
{
[StringValue("FORMS")]
FORMS = 1,
[StringValue("WINDOWS")]
WINDOWSAUTHENTICATION = 2,
[StringValue("SSO")]
SINGLESIGNON = 3
}
当然，我需要一些东西来检索StringValue:
public static class StringEnum
{
public static string GetStringValue(Enum value)
{
string output = null;
Type type = value.GetType();
//Check first in our cached results...
//Look for our 'StringValueAttribute'
//in the field's custom attributes
FieldInfo fi = type.GetField(value.ToString());
StringValue[] attrs =
fi.GetCustomAttributes(typeof(StringValue),
false) as StringValue[];
if (attrs.Length > 0)
{
output = attrs[0].Value;
}
return output;
}
}
很好，现在我已经有了工具来获取枚举器的字符串值。
然后我可以这样使用它:
string valueOfAuthenticationMethod = StringEnum.GetStringValue(AuthenticationMethod.FORMS);
好的，现在所有这些工作就像一个魅力，但我发现它有很多工作。我想知道有没有更好的解决办法。
我还尝试了一些字典和静态属性，但这也不是更好。
当我遇到这样的情况时，我提出下面的解决方案。
作为一个消费阶级，你可以有
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace MyApp.Dictionaries
{
class Greek
{
public static readonly string Alpha = "Alpha";
public static readonly string Beta = "Beta";
public static readonly string Gamma = "Gamma";
public static readonly string Delta = "Delta";
private static readonly BiDictionary<int, string> Dictionary = new BiDictionary<int, string>();
static Greek() {
Dictionary.Add(1, Alpha);
Dictionary.Add(2, Beta);
Dictionary.Add(3, Gamma);
Dictionary.Add(4, Delta);
}
public static string getById(int id){
return Dictionary.GetByFirst(id);
}
public static int getByValue(string value)
{
return Dictionary.GetBySecond(value);
}
}
}
使用双向字典:
基于此(https://stackoverflow.com/a/255638/986160)，假设键将与字典中的单个值相关联，类似于(https://stackoverflow.com/a/255630/986160)，但更优雅一些。这个字典也是可枚举的，你可以在整型和字符串之间来回切换。此外，除了这个类，你的代码库中不需要有任何字符串。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;
namespace MyApp.Dictionaries
{
class BiDictionary<TFirst, TSecond> : IEnumerable
{
IDictionary<TFirst, TSecond> firstToSecond = new Dictionary<TFirst, TSecond>();
IDictionary<TSecond, TFirst> secondToFirst = new Dictionary<TSecond, TFirst>();
public void Add(TFirst first, TSecond second)
{
firstToSecond.Add(first, second);
secondToFirst.Add(second, first);
}
public TSecond this[TFirst first]
{
get { return GetByFirst(first); }
}
public TFirst this[TSecond second]
{
get { return GetBySecond(second); }
}
public TSecond GetByFirst(TFirst first)
{
return firstToSecond[first];
}
public TFirst GetBySecond(TSecond second)
{
return secondToFirst[second];
}
public IEnumerator GetEnumerator()
{
return GetFirstEnumerator();
}
public IEnumerator GetFirstEnumerator()
{
return firstToSecond.GetEnumerator();
}
public IEnumerator GetSecondEnumerator()
{
return secondToFirst.GetEnumerator();
}
}
}
我使用系统中的Description属性。ComponentModel名称空间。简单地装饰枚举，然后使用下面的代码来检索它:
public static string GetDescription<T>(this object enumerationValue)
where T : struct
{
Type type = enumerationValue.GetType();
if (!type.IsEnum)
{
throw new ArgumentException("EnumerationValue must be of Enum type", "enumerationValue");
}
//Tries to find a DescriptionAttribute for a potential friendly name
//for the enum
MemberInfo[] memberInfo = type.GetMember(enumerationValue.ToString());
if (memberInfo != null && memberInfo.Length > 0)
{
object[] attrs = memberInfo[0].GetCustomAttributes(typeof(DescriptionAttribute), false);
if (attrs != null && attrs.Length > 0)
{
//Pull out the description value
return ((DescriptionAttribute)attrs[0]).Description;
}
}
//If we have no description attribute, just return the ToString of the enum
return enumerationValue.ToString();
}
举个例子:
public enum Cycle : int
{
[Description("Daily Cycle")]
Daily = 1,
Weekly,
Monthly
}
这段代码很好地满足了不需要“友好名称”的枚举，只返回枚举的. tostring()。
试试type-safe-enum模式。
public sealed class AuthenticationMethod {
private readonly String name;
private readonly int value;
public static readonly AuthenticationMethod FORMS = new AuthenticationMethod (1, "FORMS");
public static readonly AuthenticationMethod WINDOWSAUTHENTICATION = new AuthenticationMethod (2, "WINDOWS");
public static readonly AuthenticationMethod SINGLESIGNON = new AuthenticationMethod (3, "SSN");
private AuthenticationMethod(int value, String name){
this.name = name;
this.value = value;
}
public override String ToString(){
return name;
}
}
更新
显式(或隐式)类型转换可以通过
adding static field with mapping
private static readonly Dictionary<string, AuthenticationMethod> instance = new Dictionary<string,AuthenticationMethod>();
n.b. In order that the initialisation of the the "enum member" fields doesn't throw a NullReferenceException when calling the instance constructor, be sure to put the Dictionary field before the "enum member" fields in your class. This is because static field initialisers are called in declaration order, and before the static constructor, creating the weird and necessary but confusing situation that the instance constructor can be called before all static fields have been initialised, and before the static constructor is called.
filling this mapping in instance constructor
instance[name] = this;
and adding user-defined type conversion operator
public static explicit operator AuthenticationMethod(string str)
{
AuthenticationMethod result;
if (instance.TryGetValue(str, out result))
return result;
else
throw new InvalidCastException();
}
