枚举按位运算返回错误的值

Question

我有颜色选择enum,代表红色,蓝色,绿色和无.

[Flags]
public enum SelectedColor
{
    None, Red, Blue, Green
}

当我创建一个新的枚举并将其设置为Red和Green,然后检查是否Blue设置,则返回true. Blue从未在任何地方设置.

例如:

SelectedColor selectedColor = SelectedColor.Red;
selectedColor |= SelectedColor.Green; //Add Green to Selection

//Check if blue is set
Debug.Log("Blue Selected hasFlag? : " + hasFlag(selectedColor, SelectedColor.Blue));

//Check if blue is set
Debug.Log("Blue Selected isSet? : " + isSet(selectedColor, SelectedColor.Blue));

输出:

Blue Selected hasFlag？:错

Blue Selected isSet？:是的

hasFlag和isSet函数:

bool hasFlag(SelectedColor source, SelectedColor value)
{
    int s1 = (int)source;
    return Convert.ToBoolean((s1 & Convert.ToInt32(((int)value) == s1)));
}


bool isSet(SelectedColor source, SelectedColor critValue)
{
    //return ((source & critValue) == critValue);
    return ((source & critValue) != 0);
}

如您所见,我的isSet函数返回了错误的值.我曾经尝试都return ((source & critValue) == critValue)和return ((source & critValue) != 0);它,但他们都还是失败了.这应该根据我对SO和这篇文章的研究.

我的hasFlag功能很好,但为什么isSet函数返回错误的值？

请注意我使用的是.NET 3.5,所以我不能使用.NET 4枚举辅助函数,例如HasFlag.

Answer 1

如果您没有为枚举指定值,则会将序号分配给它们,如下所示:

[Flags]
public enum SelectedColor // WRONG
{
    None  = 0, // 000
    Red   = 1, // 001
    Blue  = 2, // 010
    Green = 3  // 011 <-- Not the next power of two!
}

然后这发生了:

selectedColor = SelectedColor.Red; // 001
selectedColor |= SelectedColor.Green; // (001 | 011 ) == 011, which is still Green

您需要为[Flags]枚举使用2的幂,如下所示:

[Flags]
public enum SelectedColor // CORRECT
{
    None  = 0, // 000
    Red   = 1, // 001
    Blue  = 2, // 010
    Green = 4  // 100
}

然后它正常工作:

selectedColor = SelectedColor.Red; // 001
selectedColor |= SelectedColor.Green; // (001 | 100) == 101, which is Red, Green