HasFlag不承认角色分配

问题描述

我用饰有[国旗]枚举控制在我的MVC2应用程序autoization。下面是我的code的例子：

I'm using an Enum decorated with [Flags] to control autoization within my MVC2 app. Below is my code examples:

[Flags]
public enum SecurityRoles
{
    None = 0,
    Executive = 1,
    BackOffice = 2,
    AccountManager = 4,
    Consultant = 8,
    Administrator = 16
}

[TestMethod]
public void MultipleSelectionsTest()
{
    var requiredRoles = SecurityRoles.Executive | SecurityRoles.BackOffice;
    var user1Roles = SecurityRoles.Executive | SecurityRoles.Administrator | SecurityRoles.BackOffice | SecurityRoles.Consultant;
    var user1HasAccess = user1Roles.HasFlag(requiredRoles);

    var user2Roles = SecurityRoles.Administrator | SecurityRoles.BackOffice | SecurityRoles.Consultant;
    var user2HasAccess = user2Roles.HasFlag(requiredRoles);


    Assert.IsTrue(user1HasAccess);  //returns true
    Assert.IsTrue(user2HasAccess);  //returns false
}

正如你所看到的，user2Roles containes的BackOffice作用和requiredRoles还含有的BackOffice作用，但是，user2HasAccess是假的。这是为什么？我在想什么？ user1HasAccess是真实的。

As you can see, user2Roles containes BackOffice role and requiredRoles also contains BackOffice role, however, user2HasAccess is false. Why is that? What am I missing? user1HasAccess is true.

推荐答案

纠正我，如果我错了（因为我可以），但是当你进行枚举标志检查，.NET本质上是做的二进制算术的一个整数，再presents的标志的总和。

Correct me if I'm wrong (because I could be), but when you perform Enum flag checks, .NET is essentially doing binary arithmetic on an integer which represents the sum of the flags.

因此​​，有 SecurityRoles.Administrator | SecurityRoles.BackOffice | SecurityRoles.Consultant 相同或二进制 11010 具有26的值。

So having SecurityRoles.Administrator | SecurityRoles.BackOffice | SecurityRoles.Consultant is the same as having a value of 26 or 11010 in binary.

当你拨打电话，以Enum.HasFlags，这是正在执行的操作是返回thisInstance和放大器;标志==标志

When you make the call to Enum.HasFlags, the operation that's being performed is return thisInstance & flag == flag

所以，如果你正在检查pviously提到的标志设置对你的要求 SecurityRoles.Executive的角色$ P $ | SecurityRoles.BackOffice 3或 11二进制，数学是这样的一个值：

So if you're checking the previously mentioned flag set against your required roles of SecurityRoles.Executive | SecurityRoles.BackOffice a value of 3 or 11 in binary, the math goes something like this:

11010 - 26 Administrator | BackOffice | Consultant
00011 -  3 Executive | BackOffice
-----
00010 -  2 BackOffice which really doesn't mean anything useful

然后，它会按照 26安培; 3 == 3 是假的。

和为求是彻底的，因为 SecurityRoles.Executive | SecurityRoles.Administrator | SecurityRoles.BackOffice | SecurityRoles.Consultant 的值27或 11011 二进制，数学是这样的：

And for the sake of being thorough, given SecurityRoles.Executive | SecurityRoles.Administrator | SecurityRoles.BackOffice | SecurityRoles.Consultant a value of 27 or 11011 in binary, the math goes like this:

11011 - 26 Executive  | Administrator | BackOffice | Consultant
00011 -  3 Executive | BackOffice
-----
00011 -  3 Executive | BackOffice

然后，它会按照 26安培; 3 == 3 是真实的。

这是扩展方法是这样的，可能是值得的（未经测试）

An extension method something like this, might be worthwhile (untested)

public static bool HasFlags(this Enum source, Enum[] flags)
{
    return flags.Any(f => source.HasFlag(f));
}

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