如何从访问掩码中读取访问权限？

Question

User can have the following access rights:

Read = 1
Create = 2
Edit = 4
Delete = 8
Publish = 16
Administer = 32

When access rights are saved in the database, only one number is used to represent all access rights for that user.

eg

3 = Read + Create
25 = Read + Delete + Publish

How can I get all access rights for a given number (access mask)?

Any help would be greatly appreciated!

Answer 1

[Flags]
public enum MyFlags
{
    Read = 1,
    Create = 2,
    Edit = 4,
    Delete = 8,
    Publish = 16,
    Administer = 32,
}

To declare

MyFlags readCreate = MyFlags.Read | MyFlags.Create;

To test

bool hasRead = (readCreate & MyFlags.Read) == MyFlags.Read;
bool hasEdit = (readCreate & MyFlags.Edit) == MyFlags.Edit;

Answer 2

var mask = (AccessRights)25;

var rightsForMask = Enum.GetValues(typeof(AccessRights))
                        .Cast<AccessRights>()
                        .Where(x => mask.HasFlag(x));

foreach (var right in rightsForMask)
{
    // displays "1:Read", "8:Delete", "16:Publish"
    Console.WriteLine((int)right + ":" + right);
}

// ...

[Flags]
public enum AccessRights
{
    Read = 1, Create = 2, Edit = 4, Delete = 8, Publish = 16, Administer = 32
}

If you're not using .NET4 then the HasFlag method won't be available, in which case you'll need to change the Where clause to read Where(x => (mask & x) == x) .