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。
我创建了一个基类，用于在. net中创建字符串值的枚举。它只是一个c#文件，你可以复制粘贴到你的项目中，或者通过名为StringEnum的NuGet包安装。GitHub回购
如果类被注释为xml comment <completitionlist>，智能感知将提示枚举名称。(适用于c#和VB)
类似于普通enum的用法:
///<completionlist cref="HexColor"/>
class HexColor : StringEnum<HexColor>
{
public static readonly HexColor Blue = Create("#FF0000");
public static readonly HexColor Green = Create("#00FF00");
public static readonly HexColor Red = Create("#000FF");
}
// Static Parse Method
HexColor.Parse("#FF0000") // => HexColor.Red
HexColor.Parse("#ff0000", caseSensitive: false) // => HexColor.Red
HexColor.Parse("invalid") // => throws InvalidOperationException
// Static TryParse method.
HexColor.TryParse("#FF0000") // => HexColor.Red
HexColor.TryParse("#ff0000", caseSensitive: false) // => HexColor.Red
HexColor.TryParse("invalid") // => null
// Parse and TryParse returns the preexistent instances
object.ReferenceEquals(HexColor.Parse("#FF0000"), HexColor.Red) // => true
// Conversion from your `StringEnum` to `string`
string myString1 = HexColor.Red.ToString(); // => "#FF0000"
string myString2 = HexColor.Red; // => "#FF0000" (implicit cast)
Instalation:
将下面的StringEnum基类粘贴到项目中。(最新版本)
或者安装StringEnum NuGet包，它基于。net Standard 1.0，所以它可以运行在。net Core >= 1.0， . net Framework >= 4.5, Mono >= 4.6等等。
/// <summary>
/// Base class for creating string-valued enums in .NET.<br/>
/// Provides static Parse() and TryParse() methods and implicit cast to string.
/// </summary>
/// <example>
/// <code>
/// class Color : StringEnum <Color>
/// {
/// public static readonly Color Blue = Create("Blue");
/// public static readonly Color Red = Create("Red");
/// public static readonly Color Green = Create("Green");
/// }
/// </code>
/// </example>
/// <typeparam name="T">The string-valued enum type. (i.e. class Color : StringEnum<Color>)</typeparam>
public abstract class StringEnum<T> : IEquatable<T> where T : StringEnum<T>, new()
{
protected string Value;
private static Dictionary<string, T> valueDict = new Dictionary<string, T>();
protected static T Create(string value)
{
if (value == null)
return null; // the null-valued instance is null.
var result = new T() { Value = value };
valueDict.Add(value, result);
return result;
}
public static implicit operator string(StringEnum<T> enumValue) => enumValue.Value;
public override string ToString() => Value;
public static bool operator !=(StringEnum<T> o1, StringEnum<T> o2) => o1?.Value != o2?.Value;
public static bool operator ==(StringEnum<T> o1, StringEnum<T> o2) => o1?.Value == o2?.Value;
public override bool Equals(object other) => this.Value.Equals((other as T)?.Value ?? (other as string));
bool IEquatable<T>.Equals(T other) => this.Value.Equals(other.Value);
public override int GetHashCode() => Value.GetHashCode();
/// <summary>
/// Parse the <paramref name="value"/> specified and returns a valid <typeparamref name="T"/> or else throws InvalidOperationException.
/// </summary>
/// <param name="value">The string value representad by an instance of <typeparamref name="T"/>. Matches by string value, not by the member name.</param>
/// <param name="caseSensitive">If true, the strings must match case and takes O(log n). False allows different case but is little bit slower (O(n))</param>
public static T Parse(string value, bool caseSensitive = true)
{
var result = TryParse(value, caseSensitive);
if (result == null)
throw new InvalidOperationException((value == null ? "null" : $"'{value}'") + $" is not a valid {typeof(T).Name}");
return result;
}
/// <summary>
/// Parse the <paramref name="value"/> specified and returns a valid <typeparamref name="T"/> or else returns null.
/// </summary>
/// <param name="value">The string value representad by an instance of <typeparamref name="T"/>. Matches by string value, not by the member name.</param>
/// <param name="caseSensitive">If true, the strings must match case. False allows different case but is slower: O(n)</param>
public static T TryParse(string value, bool caseSensitive = true)
{
if (value == null) return null;
if (valueDict.Count == 0) System.Runtime.CompilerServices.RuntimeHelpers.RunClassConstructor(typeof(T).TypeHandle); // force static fields initialization
if (caseSensitive)
{
if (valueDict.TryGetValue(value, out T item))
return item;
else
return null;
}
else
{
// slower O(n) case insensitive search
return valueDict.FirstOrDefault(f => f.Key.Equals(value, StringComparison.OrdinalIgnoreCase)).Value;
// Why Ordinal? => https://esmithy.net/2007/10/15/why-stringcomparisonordinal-is-usually-the-right-choice/
}
}
}
这里有很多很棒的答案，但在我的情况下，并没有解决我想要的“字符串enum”，这是:
可用在switch语句中，例如switch(myEnum)
可以在函数参数中使用，例如foo(myEnum类型)
可以引用，例如myEnum。FirstElement
我可以使用字符串，例如foo("FirstElement") == foo(myenumer .FirstElement)
1、2和4实际上可以用一个字符串的c#类型定义来解决(因为字符串在c#中是可切换的)
3可以通过静态const字符串来求解。所以如果你有同样的需求，这是最简单的方法:
public sealed class Types
{
private readonly String name;
private Types(String name)
{
this.name = name;
}
public override String ToString()
{
return name;
}
public static implicit operator Types(string str)
{
return new Types(str);
}
public static implicit operator string(Types str)
{
return str.ToString();
}
#region enum
public const string DataType = "Data";
public const string ImageType = "Image";
public const string Folder = "Folder";
#endregion
}
这允许例如:
public TypeArgs(Types SelectedType)
{
Types SelectedType = SelectedType
}
and
public TypeObject CreateType(Types type)
{
switch (type)
{
case Types.ImageType:
//
break;
case Types.DataType:
//
break;
}
}
CreateType可以用字符串或类型调用。然而，缺点是任何字符串都是自动有效的enum，这可以被修改，但它将需要某种init函数…或者可能使它们显式转换内部?
现在，如果一个int值对你来说很重要(也许是比较速度)，你可以使用Jakub Šturc的一些想法，做一些疯狂的事情，这是我的尝试:
public sealed class Types
{
private static readonly Dictionary<string, Types> strInstance = new Dictionary<string, Types>();
private static readonly Dictionary<int, Types> intInstance = new Dictionary<int, Types>();
private readonly String name;
private static int layerTypeCount = 0;
private int value;
private Types(String name)
{
this.name = name;
value = layerTypeCount++;
strInstance[name] = this;
intInstance[value] = this;
}
public override String ToString()
{
return name;
}
public static implicit operator Types(int val)
{
Types result;
if (intInstance.TryGetValue(val, out result))
return result;
else
throw new InvalidCastException();
}
public static implicit operator Types(string str)
{
Types result;
if (strInstance.TryGetValue(str, out result))
{
return result;
}
else
{
result = new Types(str);
return result;
}
}
public static implicit operator string(Types str)
{
return str.ToString();
}
public static bool operator ==(Types a, Types b)
{
return a.value == b.value;
}
public static bool operator !=(Types a, Types b)
{
return a.value != b.value;
}
#region enum
public const string DataType = "Data";
public const string ImageType = "Image";
#endregion
}
但是当然"Types bob = 4;"是没有意义的，除非你先对它们进行初始化，这就有点失败了……
但理论上a型== b型会更快…
选项1:
public sealed class FormsAuth
{
public override string ToString{return "Forms Authtentication";}
}
public sealed class WindowsAuth
{
public override string ToString{return "Windows Authtentication";}
}
public sealed class SsoAuth
{
public override string ToString{return "SSO";}
}
然后
object auth = new SsoAuth(); //or whatever
//...
//...
// blablabla
DoSomethingWithTheAuth(auth.ToString());
选项2:
public enum AuthenticationMethod
{
FORMS = 1,
WINDOWSAUTHENTICATION = 2,
SINGLESIGNON = 3
}
public class MyClass
{
private Dictionary<AuthenticationMethod, String> map = new Dictionary<AuthenticationMethod, String>();
public MyClass()
{
map.Add(AuthenticationMethod.FORMS,"Forms Authentication");
map.Add(AuthenticationMethod.WINDOWSAUTHENTICATION ,"Windows Authentication");
map.Add(AuthenticationMethod.SINGLESIGNON ,"SSo Authentication");
}
}
