NewtonSoft Json serializer– List Subclass with extra members in it

I have a class that looks like

public class DemoUsersList : List<DemoUser> {
    public DemoUser AdminUser;
}
public  class DemoUser {
        public int Id { get; set; }
        public string Name { get; set; }
    }

Now, I have to serialize this collection. Now, serializer got a problem! what to serialize, base class or derived class? You would end-up getting only the base class

var users = new DemoUsersList();

users.Add( new DemoUser { Id = 1, Name = "guru" });
users.Add(new DemoUser { Id = 2, Name = "aaa" });

users.AdminUser= new DemoUser{Id=0, Name="Admin"} ;

var str = JsonConvert.SerializeObject(users);
Console.WriteLine(str); 

Workaround? Just allow serializing derived class and expose the base class as a member in the serial class. Following code can do this for you.

[JsonObject(MemberSerialization=MemberSerialization.OptIn)]
public class DemoUsersList : List<DemoUser> {

    [JsonProperty]
    public IEnumerable<DemoUser> Users {
        get { return this.Select(x => x); }
    }

    [JsonProperty]
    public DemoUser AdminUser;