6

这个问题的第一个答案：当位掩码（标志）枚举太大时该怎么办正是我想要做的，只是我不知道如何使用 LINQ to SQL 将它存储在数据库中并绑定它用户无需为每个事物/逻辑组创建 2 个表。

这最好通过代码来解释（虽然不完整，但它们对 LinqPad 很友好）：

// Requirements:
// 1) Using LINQ to SQL
// 2) Track User's CRUD rights in different parts of an application (parts referred to below as 'Things')
// For example: ThingA.Create, ThingB.Read, ThingB.Update, ThingC.Delete
// Desired usage: if (User.IsAllowed(ThingA.Create)) { // allowed } else { // not allowed }
// 3) Allow for more than 64 'Things'
// 4) Do not want to refer to permissions using strings like User.IsAllowed("Create ThingA");

//
// Scenario A: This works, but you would be limited to adding only 60 'Things'
// Example usage:
// User Bob = new User();
// var desiredPermissions = Permissions.Create | Permissions.ThingA; // Permission = Unique binary value combination of flags
// if ((Bob.Permissions & desiredPermissions) == desiredPermissions) { // Bob has permission to Create ThingA
[Flags]
public enum Permissions : ulong
{
    Create = 1 << 0,
    Read = 1 << 1,
    Update = 1 << 2,
    Delete = 1 << 3,

    // Limited to 60 'Things'
    ThingA = 1 << 4,
    ThingB = 1 << 5 
}

// User Model
[Table(Name="Users")]
public class User
{
    [Column(IsPrimaryKey = true)]
    public string FName { get; set; }

    [Column]
    public Permissions Permissions { get; set; }

    public User()
    {
    }
}

场景B：

//
// Scenario B: This would work too, but each new 'Thing' would need its own flag enum list stored in its own table (ThingXPermissions),
// with another table linking ThingXPermissions.X to Users.ID (UserThingXPermissions) (yuck!)
// Would like to avoid having to change database structure when adding more 'Things' in future.

// User Model
[Table(Name="Users")]
public class User
{
    [Column(IsPrimaryKey = true, IsDbGenerated = true)]
    public int ID { get; set; }

    private EntitySet<ThingAPermissions> userThingAPermissions = new EntitySet<ThingAPermissions>();
    [Association(Name = "FK_User_UserThingAPermissions", Storage = "userThingAPermissions", OtherKey = "FK_User_Id", ThisKey = "ID")]
    public IEnumerable<ThingAPermissions> UserThingAPermissions
    { get { return userThingAPermissions; } }

    public IEnumerable<ThingAPermissions> ThingAPermissions
    { get { return (from up in UserThingAPermissions select up.UserThingAPermissions).AsEnumerable(); } }

    public User()
    {
    }
}

[Table(Name="UserThingAPermissions")]
public class UserThingAPermissions
{
    [Column(IsPrimaryKey = true)]
    public int FK_User_Id;

    private EntityRef<User> user;
    [Association(IsForeignKey = true, ThisKey = "FK_User_Id")]
    public User User
    {
        get { return user.Entity; }
        set { user.Entity = value; }
    }

    [Column]
    public ThingAPermissions ThingAPermissions { get; set; }
}

// ThingAPermissions
[Flags]
public enum ThingAPermissions : ulong
{
    Create = 1 << 0,
    Read = 1 << 1,
    Update = 1 << 2,
    Delete = 1 << 3
}

所需场景：

//
// Desired Scenario: Psuedo code of what I'd like to be able to do:
// Single Permissions (CRUD) list
// Single||simple Things list
// Single||simple table associating UserX, ThingX, PermissionX
// Example usage:
// User Bob = new User();
// var desiredPermissions = Permissions.Create | Things.ThingZ; // Permission = Unique binary value combination of flags
// if ((Bob.Permissions & desiredPermissions) == desiredPermissions) { // Bob has permission to Create ThingZ
// Missing link: Combining enums and storing into database linked to user
// e.g.
// [Table = "UserPermissions"]
// (User, Thing, Permission)
// 1, ThingZ, Create
// 1, ThingZ, Delete
// 1, ThingX, Read
// 2, ThingZ, Read
// 2, ThingX, Delete
[Flags]
public enum Permissions : ulong
{
    Create = 1 << 0,
    Read = 1 << 1,
    Update = 1 << 2,
    Delete = 1 << 3
}

[Flags]
public enum Things : ulong
{
    ThingZ = 1 << 0,
    ThingY = 1 << 1,
    ThingX = 1 << 2,
    ThingW = 1 << 3
}

[Table(Name="UserPermissions")]
public class UserPermission
{
    [Column(IsPrimaryKey = true)]
    public int FK_User_Id;

    private EntityRef<User> user;
    [Association(IsForeignKey = true, ThisKey = "FK_User_Id")]
    public User User
    {
        get { return user.Entity; }
        set { user.Entity = value; }
    }

    [Column]
    public int FK_Thing_Thing { get; set; }

    private EntityRef<Things> thing;
    [Association(IsForeignKey = true, ThisKey = "FK_User_Id")]
    public User User
    {
        get { return user.Entity; }
        set { user.Entity = value; }
    }

    [Column]
    public Permissions Permission { get; set; }
}

其他代码尝试：

使用枚举标志位的 WPF 基于权限的授权

4

1 回答 1

3

不确定您是否完全了解标志的工作原理。您使用左移运算符的原因是您的枚举将成为以下值的指数。

flag 属性是让 .NET 知道您的枚举值可以是倍数。

例如，如果您将 ThingA 和 ThingB 添加并添加它们 (48)

Console.Write((Permissions)48));

返回的值是 ThingA 和 ThingB。您只需将其保存为ulong数据库中的单个，您的代码将能够找出其余部分。

于 2014-03-11T18:31:18.020 回答