using generic list with custom class in the project settings becomes null after each run

Question

i have a program which a part of it includes registering a user and then login in with that username pass he provided when he registered every time we run the program. i know that this can be accomplished with a simple database but i want to use the project settings instead. i have a user class:

class User
{
    public string name { get; set; }
    public string username { get; set; }
    public string password { get; set; }
    public string email { get; set; }
    public User(string name, string username, string password, string email)
    {
        this.name = name;
        this.username = username;
        this.password = password;
        this.email = email;
    }
}

and then with the use of this post(from ismail-degani) in this page : Using Settings with Complex Types now i have created a list and this is the xml portion:

<Setting Name="Users" Type="System.Collections.Generic.List`1[Forum.User]" Scope="User">
  <Value Profile="(Default)" />
</Setting>

now i can access this list and in the first i new it with this(i have a count which indicates is this the first run or not)

 private void Login_Form_Load(object sender, EventArgs e)
        {
        if (Settings.Default.Count == 0)
        {
            Settings.Default.Users = new List<User>();
        }
    } 

and after adding some user to it i count++ and save it with settings.default.save() function. but after running the program again my list becomes null again but the count is working just fine. what the problem may be?

Update: this is how i add a user and save the settings:

 private void sabtuser()
    {
        User newuser = new User(tb_name.Text, tb_username.Text, tb_password.Text, tb_email.Text);
        Settings.Default.Users.Add(newuser);
        Settings.Default.Count++;
        Settings.Default.Save();
        this.Close();
    }

Answer 1

To save and reload your list of User objects to and from the settings file, you will need to make the class public and provide a default (parameter-less) constructor. (The default constructor can be private.)

public class User
{
    private User() {}

    public string name { get; set; }
    public string username { get; set; }
    public string password { get; set; }
    public string email { get; set; }
    public User(string name, string username, string password, string email)
    {
        this.name = name;
        this.username = username;
        this.password = password;
        this.email = email;
    }
}

Without the class being public, the data will not be written to the settings file.

Without the default parameter-less constructor, the data will not be read from the file again.

Answer 2

Most likely you need to change the scope of the setting to Application level instead of User level.

<Setting Name="Users" Type="System.Collections.Generic.List`1[Forum.User]" Scope="Application">
  <Value Profile="(Default)" />
</Setting>