C#枚举中使用Flags特性

这种用处很大，比如权限、执行状态等，都可以用一个int型保存到数据库中，C#中使用枚举可以处理这个问题。

    [Flags]
    public enum Permission
    {
        create = 1,
        read = 2,
        update = 4,
        delete = 8,        
    }

C#对该类型的操作如下：

            Permission permission = Permission.create | Permission.read | Permission.update | Permission.delete;
            Console.WriteLine("1、枚举创建，并赋值……");
            Console.WriteLine(permission.ToString());
            Console.WriteLine((int)permission);

            permission = (Permission)Enum.Parse(typeof(Permission), "5");
            Console.WriteLine("2、通过数字字符串转换……");
            Console.WriteLine(permission.ToString());
            Console.WriteLine((int)permission);

            permission = (Permission)Enum.Parse(typeof(Permission), "update, delete, read", true);
            Console.WriteLine("3、通过枚举名称字符串转换……");
            Console.WriteLine(permission.ToString());
            Console.WriteLine((int)permission);

            permission = (Permission)7;
            Console.WriteLine("4、直接用数字强制转换……");
            Console.WriteLine(permission.ToString());
            Console.WriteLine((int)permission);

            permission = permission & ~Permission.read;
            Console.WriteLine("5、去掉一个枚举项……");
            Console.WriteLine(permission.ToString());
            Console.WriteLine((int)permission);

            permission = permission|Permission.delete;
            Console.WriteLine("6、加上一个枚举项……");
            Console.WriteLine(permission.ToString());
            Console.WriteLine((int)permission);

在数据库中判断：

AND (@permission IS NULL OR @permission=0 OR permission &@permission =@permission)

上面的sql语句同样可以判断多个权限