在c＃中扩展枚举

在java中我用来扩展枚举值或重写这样的方法：

enum SomeEnum { option1("sv") { public String toString() { return "Some value"; } }, option2; private String PassedValue; public SomeEnum(String somevalue) { this.PassedValue = somevalue; } public SomeEnum() { this.PassedValue = "Default Value"; } public String getPassedValue() { return this.PassedValue; } } 

有没有办法在c＃中做类似的事情，或者c＃中的枚举更有限

Answer 1

我希望枚解在.Net中更强大。 我喜欢.Net！ 您可以使用属性来完成同样的事情。 写下面的代码一次，到处使用它。 这将是一个很长的答案，但我认为这是一个非常好的解决方案，所以要有耐心！

用法

 SomeEnum e = SomeEnum.ValueTwo; string description = e.GetDescription(); 

恩欧姆

使用属性来描述枚举及其值。

 [DescriptiveEnumEnforcement(DescriptiveEnumEnforcement.EnforcementTypeEnum.ThrowException)] public enum SomeEnum { [Description("Value One")] ValueOne, [Description("Value Two")] ValueTwo, [Description("Value 3")] ValueThree } 

DescriptionAttribute

 /// 
Indicates that an enum value has a description.
 [AttributeUsage(AttributeTargets.Field)] public class DescriptionAttribute : System.Attribute { /// 
The description for the enum value.
 public string Description { get; set; } /// 
Constructs a new DescriptionAttribute.
 public DescriptionAttribute() { } /// 
Constructs a new DescriptionAttribute.
 /// The initial value of the Description property. public DescriptionAttribute(string description) { this.Description = description; } /// 
Returns the Description property.
 /// The Description property. public override string ToString() { return this.Description; } } 

DescriptiveEnumEnforcementAttribute

确保正确配置枚举的属性。

 /// 
Indicates whether or not an enum must have a NameAttribute and a DescriptionAttribute.
 [AttributeUsage(AttributeTargets.Enum)] public class DescriptiveEnumEnforcementAttribute : System.Attribute { /// 
Defines the different types of enforcement for DescriptiveEnums.
 public enum EnforcementTypeEnum { /// 
Indicates that the enum must have a NameAttribute and a DescriptionAttribute.
 ThrowException, /// 
Indicates that the enum does not have a NameAttribute and a DescriptionAttribute, the value will be used instead.
 DefaultToValue } /// 
The enforcement type for this DescriptiveEnumEnforcementAttribute.
 public EnforcementTypeEnum EnforcementType { get; set; } /// 
Constructs a new DescriptiveEnumEnforcementAttribute.
 public DescriptiveEnumEnforcementAttribute() { this.EnforcementType = EnforcementTypeEnum.DefaultToValue; } /// 
Constructs a new DescriptiveEnumEnforcementAttribute.
 /// The initial value of the EnforcementType property. public DescriptiveEnumEnforcementAttribute(EnforcementTypeEnum enforcementType) { this.EnforcementType = enforcementType; } } 

获得描述

 /// 
Provides functionality to enhance enumerations.
 public static partial class EnumUtil { /// 
Returns the description of the specified enum.
 /// The value of the enum for which to return the description. /// A description of the enum, or the enum name if no description exists. public static string GetDescription(this Enum value) { return GetEnumDescription(value); } /// 
Returns the description of the specified enum.
 /// The value of the enum for which to return the description. /// A description of the enum, or the enum name if no description exists. public static string GetDescription(object value) { return GetEnumDescription(value); } /// 
Returns the description of the specified enum.
 /// The value of the enum for which to return the description. /// A description of the enum, or the enum name if no description exists. public static string GetEnumDescription(object value) { if (value == null) return null; Type type = value.GetType(); //Make sure the object is an enum. if (!type.IsEnum) throw new ApplicationException("Value parameter must be an enum."); FieldInfo fieldInfo = type.GetField(value.ToString()); object[] descriptionAttributes = fieldInfo.GetCustomAttributes(typeof(DescriptionAttribute), false); //If no DescriptionAttribute exists for this enum value, check the DescriptiveEnumEnforcementAttribute and decide how to proceed. if (descriptionAttributes == null || descriptionAttributes.Length == 0) { object[] enforcementAttributes = fieldInfo.GetCustomAttributes(typeof(DescriptiveEnumEnforcementAttribute), false); //If a DescriptiveEnumEnforcementAttribute exists, either throw an exception or return the name of the enum instead. if (enforcementAttributes != null && enforcementAttributes.Length == 1) { DescriptiveEnumEnforcementAttribute enforcementAttribute = (DescriptiveEnumEnforcementAttribute)enforcementAttributes[0]; if (enforcementAttribute.EnforcementType == DescriptiveEnumEnforcementAttribute.EnforcementTypeEnum.ThrowException) throw new ApplicationException("No Description attributes exist in enforced enum of type '" + type.Name + "', value '" + value.ToString() + "'."); return GetEnumName(value); } else //Just return the name of the enum. return GetEnumName(value); } else if (descriptionAttributes.Length > 1) throw new ApplicationException("Too many Description attributes exist in enum of type '" + type.Name + "', value '" + value.ToString() + "'."); //Return the value of the DescriptionAttribute. return descriptionAttributes[0].ToString(); } } 

Answer 2

C＃中的枚举仅适用于（整数）值; 他们不能像Java那样拥有特殊的方法或构造函数。

但是，您可以定义对枚举起作用的扩展方法，以实现几乎相同的效果：

 public enum MyEnum { Foo = 1, Bar = 2, Default = Foo } public static class MyEnumExtensions { public static Widget ToWidget(this MyEnum enumValue) { switch (enumValue) { case MyEnum.Foo: return new Widget("Foo!"); case MyEnum.Bar: return new Widget("Bar..."); default: return null; } } } 

然后你可以说：

 var val = MyEnum.Foo; var widget = val.ToWidget(); 

Answer 3

C＃中的枚举基本上只是命名基元。 它们通常基于int ，但可以基于任何数字原语。 因此，C＃几乎不提供Java枚举所具有的function。 权衡是C＃枚举更轻，而Java枚举是完全成熟的对象。

 public enum FooBar : int { Foo = 1, Bar = 2 } 

上面的枚举与int没什么不同，除了我们现在可以使用FooBar.Foo而不是文字1 。 你可以在int之间来回转换Enum ， Enum有一些辅助function，可以在使用枚举时提供帮助。 但这就是C＃，它们很像C或C ++枚举。

Answer 4

您可以使用Extension方法在C＃中执行类似的操作。

 enum Test { Value1, Value2, Value3 } static class TextExtensions { public static string Value(this Test value) { string stringValue = default(String); switch (value) { case Test.Value1: { stringValue = "some value 1"; } break; case Test.Value2: { stringValue = "some value 2"; }; break; case Test.Value3: { stringValue = "some value 3"; }; break; } return stringValue; } } class Program { static void Main(string[] args) { Console.Write(Test.Value1.Value()); Console.ReadLine(); } }