获取列表< string>我的枚举属性使用通用方法 [英] Get a List<string> of my enum attributes with a generic method

问题描述

开始时，我们有这个基本的枚举。

At start, we have this basic enum.

public enum E_Levels {

    [ValueOfEnum("Low level")]
    LOW,

    [ValueOfEnum("Normal level")]
    NORMAL,

    [ValueOfEnum("High level")]
    HIGH
}

我想得到一个列表< string> 无论枚举。像 Extensions.GetValuesOfEnum< E_Levels>（）可能会返回一个列表< string> 与低级 正常级别和高级别中。

And I would like to get a List<string> whatever the enum. Something like Extensions.GetValuesOfEnum<E_Levels>() which could return a List<string> with "Low level", "Normal level" and "High level" in it.

StackOF帮助我获取一个值属性：

StackOF helped me to get one value attribute :

public static class Extensions {

    public static string ToValueOfEnum(this Enum value) {

        FieldInfo fieldInfo = value.GetType().GetField(value.ToString());
        ValueOfEnum[] attribs = fieldInfo.GetCustomAttributes(typeof(ValueOfEnum), false) as ValueOfEnum[];
        return attribs.Length > 0 ? attribs[0].value : null;
    }
}

我可以调用此方法无论枚举： code> E_Levels.LOW.ToValueOfEnum（）。

And I can call this method whatever the enum : E_Levels.LOW.ToValueOfEnum().

此外，StackOF帮助我获得一个列表< ; 特定枚举的字符串>
我在控制器中做了这个方法：

Furthermore, StackOF helped me to get a List<string> for a specific enum. I made this method in a controller :

private List<string> GetLevels() {

List<string> levelsToReturn = new List<string>();
var levels = Enum.GetValues(typeof(E_Levels)).Cast<E_Levels>();
foreach(E_Levels l in levels) 
    levelsToReturn.Add(l.ToValueOfEnum());

return levelsToReturn;
}

但是，这样需要我为每个枚举重写相同的方法。 />
所以我试图添加这个泛型方法我的类Extensions：

But this way requires me to rewrite the same method for each enum.
So I tried to add this generic method my class Extensions :

public static class Extensions {

    public static string ToValueOfEnum(this Enum value) {...}

    public static List<string> GetValuesOf<T>() {

        List<string> levelsToReturn = new List<string>();
        var levels = Enum.GetValues(typeof(T)).Cast<T>();
        foreach(T l in levels) 
        levelsToReturn.Add(l.ToValueOfEnum());

        return levelsToReturn;
    }
}

但是在我的foreach中， .ToValueOfEnum（）是一个未知的方法。


所以我很麻烦，我希望我可以找到一种方法，每次都不会重复使用相同的方法枚举...

But in my foreach, .ToValueOfEnum() is an unknown method.

So I am in trouble, I hoped I could find a way to not rewrite again and again the same method for each enum...

推荐答案

让我们尽量保持这个更通用的目的。

Let's try to keep this more general purpose.

我有一个扩展方法，可以从枚举值中获取属性。这将让您快速访问属性。

I have an extension method that could grab attributes off of enum values. This would give you quick access to the attributes.

public static class EnumExtensions
{
    public static TAttribute GetAttribute<TAttribute>(this Enum value)
        where TAttribute : Attribute
    {
        var type = value.GetType();
        var name = Enum.GetName(type, value);
        return type.GetField(name)
            .GetCustomAttributes(false)
            .OfType<TAttribute>()
            .SingleOrDefault();
    }
}

使用这个，你可以创建一些查询来获取什么你想要。

Using this, you could create some queries to get what you want.

var valuesOfLevels =
    Enum.GetValues(typeof(E_Levels)).Cast<E_Levels>()
        .Select(level => level.GetAttribute<ValueOfEnumAttribute>().Value);

所以你的 GetValuesOf（）方法不是一个这样的专业方法的伟大的名字IMHO）可以这样写：

So your GetValuesOf() method (which is not a great name for such a specialty method IMHO) can be written like this:

public static List<string> GetValuesOf<TEnum>()
    where TEnum : struct // can't constrain to enums so closest thing
{
    return Enum.GetValues(typeof(TEnum)).Cast<Enum>()
               .Select(val => val.GetAttribute<ValueOfEnumAttribute>().Value)
               .ToList();
}

现在你可以这样调用方法：

Now you may call the method like so:

var levelValues = GetValueOf<E_Levels>();
// levelValues = { "Low level", "Normal level", "High level" }

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