C# 4.0 扩展和枚举类型
我正在尝试向枚举类型添加扩展方法,但下面的代码失败。编译器在第C# 4.0 扩展和枚举类型,c#-4.0,enums,extension-methods,C# 4.0,Enums,Extension Methods,我正在尝试向枚举类型添加扩展方法,但下面的代码失败。编译器在第StoreType.GetAllItems行给出错误,如何将扩展方法添加到枚举类型 namespace ConsoleApplication1 { public static class EnumExtensions { public static IEnumerable<T> GetAllItems<T>(this Enum value) {
StoreType.GetAllItems
行给出错误,如何将扩展方法添加到枚举类型
namespace ConsoleApplication1
{
public static class EnumExtensions
{
public static IEnumerable<T> GetAllItems<T>(this Enum value)
{
foreach (object item in Enum.GetValues(typeof(T)))
{
yield return (T)item;
}
}
}
class Program
{
[Flags]
public enum StoreType
{
Paypal = 1,
Plimus = 2,
Other = 3
};
static void Main(string[] args)
{
StoreType.GetAllItems //Fail here
}
}
}
命名空间控制台应用程序1
{
公共静态类枚举扩展
{
公共静态IEnumerable GetAllItems(此枚举值)
{
foreach(Enum.GetValues(typeof(T))中的对象项)
{
收益回报(T)项;
}
}
}
班级计划
{
[旗帜]
公共枚举存储类型
{
贝宝=1,
Plimus=2,
其他=3
};
静态void Main(字符串[]参数)
{
StoreType.GetAllItems//此处失败
}
}
}
必须对值而不是类型调用GetAllItems:
StoreType.Paypal.GetAllItems()
但如果不将其作为扩展方法并声明为:
public static class EnumExtensions
{
public static IEnumerable<T> GetAllItems<T>()
{
foreach (object item in Enum.GetValues(typeof(T)))
{
yield return (T)item;
}
}
}
static void Main(string[] args)
{
var allEnumItems = EnumExtensions.GetAllItems<StoreType>()
}
之后,您可以使用Enum.TryParse(…)将名称解析回Enum,我认为这是您想要的?您会看到编译器错误,因为您无法覆盖默认的c#Enum,请尝试通过将方法添加到自定义类来覆盖您的Enum:
public class MyEnum
{
public static readonly MyEnum A = new MyEnum("A");
public static readonly MyEnum B = new MyEnum("B");
public static readonly MyEnum C = new MyEnum("C");
public static IEnumerable<T> GetAllItems<T>(this Enum value)
{
foreach (object item in Enum.GetValues(typeof(T)))
{
yield return (T)item;
}
}
public override string ToString()
{
return Value;
}
protected MyEnum(string value)
{
this.Value = value;
}
public string Value { get; private set; }
}
public sealed class MyDerivedEnum : MyEnum
{
public static readonly MyDerivedEnum D = new MyDerivedEnum("D");
private MyDerivedEnum(string value)
: base(value)
{
}
}
class Program
{
static void Main(string[] args)
{
MyEnum blah = MyEnum.A;
System.Console.WriteLine(blah);
blah = MyDerivedEnum.D;
System.Console.WriteLine(blah);
}
}
公共类MyEnum
{
公共静态只读MyEnum A=新MyEnum(“A”);
public static readonly MyEnum B=新的MyEnum(“B”);
public static readonly MyEnum C=新的MyEnum(“C”);
公共静态IEnumerable GetAllItems(此枚举值)
{
foreach(Enum.GetValues(typeof(T))中的对象项)
{
收益回报(T)项;
}
}
公共重写字符串ToString()
{
返回值;
}
受保护的MyEnum(字符串值)
{
这个。值=值;
}
公共字符串值{get;private set;}
}
公共密封类MyDerivedEnum:MyEnum
{
公共静态只读MyDerivedEnum D=新MyDerivedEnum(“D”);
私有MyDerivedEnum(字符串值)
:基准(值)
{
}
}
班级计划
{
静态void Main(字符串[]参数)
{
MyEnum blah=MyEnum.A;
系统控制台写入线(blah);
blah=MyDerivedEnum.D;
系统控制台写入线(blah);
}
}
我认为这是一个带有伪扩展的类。可能是这样的:
用法:
List<HttpStatusCode> list = EnumUtils<HttpStatusCode>.ToList();
Dictionary<int, HttpStatusCode> map = EnumUtils<HttpStatusCode>.ToDictionary();
List List=EnumUtils.ToList();
Dictionary map=enumultils.ToDictionary();
伪扩展类:
/// <summary>Pseudo extension class for enumerations</summary>
/// <typeparam name="TEnum">Enumeration type</typeparam>
public class EnumUtils<TEnum> where TEnum : struct, IConvertible
{
public static List<TEnum> ToList()
{
var enumType = typeof(TEnum);
return enumType.IsEnum
? enumType.GetEnumValues().OfType<TEnum>().ToList()
: throw new ArgumentException($"{enumType.Name} is not enum");
}
public static Dictionary<int, TEnum> ToDictionary()
{
Type enumType = typeof(TEnum);
return enumType.IsEnum
? enumType.GetEnumValues().OfType<TEnum>().ToDictionary(
e => Convert.ToInt32(Enum.Parse(typeof(TEnum), e.ToString()) as Enum),
e => e)
: throw new ArgumentException($"{enumType.Name} is not enum");
}
}
///枚举的伪扩展类
///枚举类型
公共类枚举,其中TEnum:struct,IConvertible
{
公共静态列表ToList()
{
var enumType=typeof(TEnum);
返回enumType.IsEnum
?enumType.GetEnumValues().OfType().ToList()
:抛出新ArgumentException($“{enumType.Name}不是枚举”);
}
公共静态字典ToDictionary()
{
类型enumType=typeof(TEnum);
返回enumType.IsEnum
?enumType.GetEnumValues().OfType().ToDictionary(
e=>Convert.ToInt32(Enum.Parse(typeof(TEnum),e.ToString())作为Enum),
e=>e)
:抛出新ArgumentException($“{enumType.Name}不是枚举”);
}
}
享受吧
/// <summary>Pseudo extension class for enumerations</summary>
/// <typeparam name="TEnum">Enumeration type</typeparam>
public class EnumUtils<TEnum> where TEnum : struct, IConvertible
{
public static List<TEnum> ToList()
{
var enumType = typeof(TEnum);
return enumType.IsEnum
? enumType.GetEnumValues().OfType<TEnum>().ToList()
: throw new ArgumentException($"{enumType.Name} is not enum");
}
public static Dictionary<int, TEnum> ToDictionary()
{
Type enumType = typeof(TEnum);
return enumType.IsEnum
? enumType.GetEnumValues().OfType<TEnum>().ToDictionary(
e => Convert.ToInt32(Enum.Parse(typeof(TEnum), e.ToString()) as Enum),
e => e)
: throw new ArgumentException($"{enumType.Name} is not enum");
}
}