How to orderBy Date or find record with oldest date in custom class?

Console App added User class

public class User
{
    public string UserName { get; set; }
    public int Count { get; set; }
    public DateTime LastSeen { get; set; }

    public User(string userName, int count, DateTime lastSeen)
    {
        UserName = userName;
        Count = count;
        LastSeen = lastSeen;
    }
}

So create List of User in Main and populate with entry from console.Read

 static void Main(string[] args)
        {
            List<User> Allusers = new List<User>();

            while (true)
           {
                Console.WriteLine("Please enter name");
                string userName = Console.ReadLine();

                if (userName == "end")
                {
                    break;
                }

                if(Allusers.Count == 0)
                {
                    User newUser = new User(userName, 1, DateTime.UtcNow);
                    Allusers.Add(newUser);
                }
                else if(Allusers.Count < 5)
                {
                    User userExist = Allusers.Find(x => x.UserName == userName);
                    if(userExist != null)
                    {
                        userExist.Count++;
                        userExist.LastSeen = DateTime.UtcNow;
                    }
                    else
                    {
                        User newUser = new User(userName, 1, DateTime.UtcNow);
                        Allusers.Add(newUser);
                    }
                }
                else
                {

//can only hold 5 records
//so here I want to find the record with the earliest date so I can remove it?
How can I do a search or a where or a find?

where date is the oldest?

order by ascending?

cant find it…

so how do I say

  User oldestUser = Allusers.Find(x => x.LastSeen == //IS OLDEST DATE).firstOrDefault();
Allusers.Remove(oldestUser );

>Solution :

If you are using Linq you could do this: AllUser.OrderByDescending(x => x.LastSeen).First() That will be the first element in the list after ordering descending.

User oldestUser = Allusers.OrderByDescending(x => x.LastSeen).FirstOrDefault();
Allusers.Remove(oldestUser);