从 int 获取枚举值

Question

如何从 int 输入中获取枚举值？假设我在下面有这个枚举。

[Flags]
public enum Weeks
{
    Sunday = 1,
    Monday = 2,
    Tuesday = 4,
    Wednesday = 8,
    Thursday = 16,
    Friday = 32,
    Saturday = 64
}

public List<Weeks> GetEnumValues(int input)
{
    // Don't know what is the logic here
    // Help is much appreciated
}

则输出如下

Examples:
1.) input = 3; This means Sunday and Monday hence 1 + 2 = 3; This should return List<Weeks> { Sunday, Monday }
2.) input = 20; This means Tuesday and Thursday hence 4 + 16 = 20; This should return List<Weeks> { Tuesday, Thursday }
3.) input = 40; This means Wednesday and Friday hence 8 + 32 = 40; This should return List<Weeks> { Wednesday, Friday }

提前致谢。

Answer 1

您可以通过循环每个枚举 "flag" 并检查每个 "flag" 是否在您的输入值中设置了该位来执行此操作。这是执行此操作的一种方法：

public List<Weeks> GetEnumValues(int input)
{
    Weeks inputEnum = (Weeks)input;
    var list = new List<Weeks>();

    foreach(var enumFlag in Enum.GetValues(typeof(Weeks)).Cast<Weeks>())
    {
        if (inputEnum.HasFlag(enumFlag))
        {
            list.Add(enumFlag);
        }
    }

    return list;
}

Answer 2

另一种方法 - 利用 Flags 枚举上的 ToString 构建逗号分隔的值列表这一事实。然后我们可以通过 Enum.Parse:

将每个元素转换回枚举值

public List<Weeks> GetEnumValues(int input)
{
    return ((Weeks)input)
         .ToString()
         .Split(',')
         .Select(day => Enum.Parse(typeof(Weeks), day))
         .ToList();
}

选择权在你...

Answer 3

@sstan 的回答是正确的，我投了答案。但我只想分享他的解决方案中我的简短版本。

public List<Weeks> GetEnumValues(int input)
{
    Weeks inputEnum = (Weeks)input;
    return Enum.GetValues(typeof(Weeks)).Cast<Weeks>().Where(x => inputEnum.HasFlag(x)).ToList();
}

从 int 获取枚举值

Get Enum Values from int

c#

bitwise-operators