c# - 如何在 .NET 枚举中搜索正确的方法

Question

我想给我的“用户”对象一些权限。该权限在枚举中定义。为了更容易理解，我将发布我的代码。

public  class User
{
   public string UserName { get; set; }
   public string Password { get; set; }
   public UserRights Permissions { get; set; }

   public override string ToString()
   {
       return "Username: " + UserName + " - Password: " + Password + " - Permisssions: " + Permissions;
   }
}

public enum UserRights
{
    Admin,
    SmallAdmin,
    SimpleUser,
    JustDummy
}

public class EnumFinder
{
    public List<User> Users = new List<User>();

    public EnumFinder()
    {
        CreateUsers();

        List<User> search = (from a in Users where a.Permissions == UserRights.SimpleUser select a).ToList<User>();
        foreach (User user in search)
        {
            Console.WriteLine(user.ToString());
        }
    }

    /// <summary>
    ///     Create some example users and put the objects into User's list
    /// </summary>
    private void CreateUsers()
    {
        var user1 = new User();
        user1.UserName = "user1";
        user1.Password = "password1";
        user1.Permissions = UserRights.Admin;

        var user2 = new User();
        user2.UserName = "user2";
        user2.Password = "password2";
        user2.Permissions = UserRights.SmallAdmin | UserRights.JustDummy;

        var user3 = new User();
        user3.UserName = "user3";
        user3.Password = "password3";
        user3.Permissions = UserRights.SimpleUser;
        Users.Add(user1);
        Users.Add(user2);
        Users.Add(user3);
    }
}

因此，如您所见，我在我的用户列表中添加了一些示例用户。他们每个人都有不同的权限。现在假设我想搜索每个具有“管理员”权限的用户。这很好用(对于那个用户):

List<User> search = (from a in Users where a.Permissions == UserRights.Admin select a).ToList<User>();

但是假设我正在寻找具有 SmallAdmin 权限的用户。所以我试了一下:

    List<User> search = (from a in Users where a.Permissions == UserRights.SmallAdmin select a).ToList<User>();

在这种情况下，没有找到用户。为什么不？感谢您的帮助。

Answer 1

用[Flags] 属性标记您的枚举并使用HasFlag方法代替

List<User> search = (from a in Users 
                     where a.Permissions.HasFlag(UserRights.SmallAdmin)
                     select a).ToList<User>();