Question

假设我有一个接受使用Flags属性修饰的枚举的函数。如果枚举的值是多个枚举元素的组合，我如何随机提取其中一个元素？我有以下但似乎必须有更好的方法。

[Flags]
enum Colours
{
    Blue = 1,
    Red = 2,
    Green = 4
}

public static void Main()
{
    var options = Colours.Blue | Colours.Red | Colours.Green;
    var opts = options.ToString().Split(',');
    var rand = new Random();
    var selected = opts[rand.Next(opts.Length)].Trim();
    var myEnum = Enum.Parse(typeof(Colours), selected);
    Console.WriteLine(myEnum);
    Console.ReadLine();
}

Answer 1

您可以调用Enum.GetValues来获取枚举定义值的数组，如下所示：

var rand = new Random();

Colors[] allValues = (Colors[])Enum.GetValues(typeof(Colors));
Colors value = allValues[rand.Next(allValues.Length)];

Answer 2

var options = Colours.Blue | Colours.Green;

var matching = Enum.GetValues(typeof(Colours))
                   .Cast<Colours>()
                   .Where(c => (options & c) == c)    // or use HasFlag in .NET4
                   .ToArray();

var myEnum = matching[new Random().Next(matching.Length)];

Answer 3

如果你不介意一点点强制转换，并且你的枚举是基础int类型，那么以下内容将起作用并且速度很快。

var rand = new Random();
const int mask = (int)(Colours.Blue | Colours.Red | Colours.Green);
return (Colours)(mask & (rand.Next(mask) + 1));

如果您只想设置一个标志，则可以执行以下操作：

var rand = new Random();
return (Colours)(0x1 << (rand.Next(3)));

Answer 4

如果我理解正确，问题是关于从标志枚举值返回一个随机枚举值，而不是从标志枚举中返回一个随机成员。

    [Flags]
    private enum Shot
    {
        Whisky = 1,
        Absynthe = 2,
        Pochin = 4,
        BrainEraser = Whisky | Absynthe | Pochin
    }

    [Test]
    public void Test()
    {
        Shot myCocktail = Shot.Absynthe | Shot.Whisky;

        Shot randomShotInCocktail = GetRandomShotFromCocktail(myCocktail);
    }

    private static Shot GetRandomShotFromCocktail(Shot cocktail)
    {
        Random random = new Random();

        Shot[] cocktailShots = Enum.GetValues(typeof(Shot)).
           Cast<Shot>().
           Where(x => cocktail.HasFlag(x)).ToArray();

        Shot randomShot = cocktailShots[random.Next(0, cocktailShots.Length)];

        return randomShot;
    }

修改

显然你应该检查枚举是否是有效值，例如：

Shot myCocktail = (Shot)666;

修改

简化

Answer 5

在我的情况下-我的枚举缺少成员，例如0x01, 0x02, 0x08，而大型ulong枚举的最大值为0x200000000。

此代码适用于我所有的情况：

/// <summary>
///     Gets <see cref="System.Random"/> instance.
/// </summary>
public static Random Random { get; } = new Random(Guid.NewGuid().GetHashCode());

/// <summary>
///     Gets random combination of Flags Enum.
/// </summary>
/// <typeparam name="T">Enum type.</typeparam>
/// <returns>Random Flags Enum combination.</returns>
public static T GetRandomFlagsEnumValue<T>()
    where T : Enum
{
    var allValues = (T[])Enum.GetValues(typeof(T));

    ulong numberValue = allValues.OrderBy(x => Random.Next())
        .Take(GetRandomInteger(1, allValues.Length - 1))
        .Select(e => Convert.ToUInt64(e, CultureInfo.InvariantCulture))
        .Aggregate((a, c) => a + c);

    return (T)Enum.ToObject(typeof(T), numberValue);
}

Flags枚举的随机值

5 个答案: