本文介绍了我们可以定义在C＃中枚举隐式转换？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
是否有可能在C＃中定义枚举的隐式转换？
Is it possible to define an implicit conversion of enums in c#?
东西，可以做到这一点？
something that could achieve this?
public enum MyEnum
{
one = 1, two = 2
}
MyEnum number = MyEnum.one;
long i = number;
如果没有，为什么不呢？
If not, why not?
有关此进一步的讨论和想法，我跟了我目前是如何处理这个问题：的
For further discussion and ideas on this, I followed up with how I currently handle this: Improving the C# enum
推荐答案
有一个解决方案。考虑以下几点：
There is a solution. Consider the following:
public sealed class AccountStatus
{
public static readonly AccountStatus Open = new AccountStatus(1);
public static readonly AccountStatus Closed = new AccountStatus(2);
public static readonly SortedList<byte, AccountStatus> Values = new SortedList<byte, AccountStatus>();
private readonly byte Value;
private AccountStatus(byte value)
{
this.Value = value;
Values.Add(value, this);
}
public static implicit operator AccountStatus(byte value)
{
return Values[byte];
}
public static implicit operator byte(AccountStatus value)
{
return value.Value;
}
}
以上提供的隐式转换：
The above offers implicit conversion:
AccountStatus openedAccount = 1; // Works
byte openedValue = AccountStatus.Open; // Works
这是不是宣告一个正常的枚举（虽然你可以重构上面的一些成一个共同的通用基类）更公平一点的工作。你可以更进一步通过使基类实现IComparable＆安培; IEquatable，以及添加方法返回DescriptionAttributes的值，声明的名称等，等
This is a fair bit more work than declaring a normal enum (though you can refactor some of the above into a common generic base class). You can go even further by having the base class implement IComparable & IEquatable, as well as adding methods to return the value of DescriptionAttributes, declared names, etc, etc.
我写了一个基类（RichEnum＆LT;>）来处理大部分FO繁重的工作，从而简化枚举上述声明下来：
I wrote a base class (RichEnum<>) to handle most fo the grunt work, which eases the above declaration of enums down to:
public sealed class AccountStatus : RichEnum<byte, AccountStatus>
{
public static readonly AccountStatus Open = new AccountStatus(1);
public static readonly AccountStatus Closed = new AccountStatus(2);
private AccountStatus(byte value) : base (value)
{
}
public static implicit operator AccountStatus(byte value)
{
return Convert(value);
}
}
基类（RichEnum）如下。
The base class (RichEnum) is listed below.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
using System.Resources;
namespace Ethica
{
using Reflection;
using Text;
[DebuggerDisplay("{Value} ({Name})")]
public abstract class RichEnum<TValue, TDerived>
: IEquatable<TDerived>,
IComparable<TDerived>,
IComparable, IComparer<TDerived>
where TValue : struct , IComparable<TValue>, IEquatable<TValue>
where TDerived : RichEnum<TValue, TDerived>
{
#region Backing Fields
/// <summary>
/// The value of the enum item
/// </summary>
public readonly TValue Value;
/// <summary>
/// The public field name, determined from reflection
/// </summary>
private string _name;
/// <summary>
/// The DescriptionAttribute, if any, linked to the declaring field
/// </summary>
private DescriptionAttribute _descriptionAttribute;
/// <summary>
/// Reverse lookup to convert values back to local instances
/// </summary>
private static SortedList<TValue, TDerived> _values;
private static bool _isInitialized;
#endregion
#region Constructors
protected RichEnum(TValue value)
{
if (_values == null)
_values = new SortedList<TValue, TDerived>();
this.Value = value;
_values.Add(value, (TDerived)this);
}
#endregion
#region Properties
public string Name
{
get
{
CheckInitialized();
return _name;
}
}
public string Description
{
get
{
CheckInitialized();
if (_descriptionAttribute != null)
return _descriptionAttribute.Description;
return _name;
}
}
#endregion
#region Initialization
private static void CheckInitialized()
{
if (!_isInitialized)
{
ResourceManager _resources = new ResourceManager(typeof(TDerived).Name, typeof(TDerived).Assembly);
var fields = typeof(TDerived)
.GetFields(BindingFlags.Static | BindingFlags.GetField | BindingFlags.Public)
.Where(t => t.FieldType == typeof(TDerived));
foreach (var field in fields)
{
TDerived instance = (TDerived)field.GetValue(null);
instance._name = field.Name;
instance._descriptionAttribute = field.GetAttribute<DescriptionAttribute>();
var displayName = field.Name.ToPhrase();
}
_isInitialized = true;
}
}
#endregion
#region Conversion and Equality
public static TDerived Convert(TValue value)
{
return _values[value];
}
public static bool TryConvert(TValue value, out TDerived result)
{
return _values.TryGetValue(value, out result);
}
public static implicit operator TValue(RichEnum<TValue, TDerived> value)
{
return value.Value;
}
public static implicit operator RichEnum<TValue, TDerived>(TValue value)
{
return _values[value];
}
public static implicit operator TDerived(RichEnum<TValue, TDerived> value)
{
return value;
}
public override string ToString()
{
return _name;
}
#endregion
#region IEquatable<TDerived> Members
public override bool Equals(object obj)
{
if (obj != null)
{
if (obj is TValue)
return Value.Equals((TValue)obj);
if (obj is TDerived)
return Value.Equals(((TDerived)obj).Value);
}
return false;
}
bool IEquatable<TDerived>.Equals(TDerived other)
{
return Value.Equals(other.Value);
}
public override int GetHashCode()
{
return Value.GetHashCode();
}
#endregion
#region IComparable Members
int IComparable<TDerived>.CompareTo(TDerived other)
{
return Value.CompareTo(other.Value);
}
int IComparable.CompareTo(object obj)
{
if (obj != null)
{
if (obj is TValue)
return Value.CompareTo((TValue)obj);
if (obj is TDerived)
return Value.CompareTo(((TDerived)obj).Value);
}
return -1;
}
int IComparer<TDerived>.Compare(TDerived x, TDerived y)
{
return (x == null) ? -1 :
(y == null) ? 1 :
x.Value.CompareTo(y.Value);
}
#endregion
public static IEnumerable<TDerived> Values
{
get
{
return _values.Values;
}
}
public static TDerived Parse(string name)
{
foreach (TDerived value in _values.Values)
if (0 == string.Compare(value.Name, name, true) || 0 == string.Compare(value.DisplayName, name, true))
return value;
return null;
}
}
}
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