C＃写入属性但没有返回值

Question

制作Windows窗体棋盘游戏，用户可以选择难度。此代码将检查用户是否已选择难度，然后将此难度写入属性。

if (combo_difficulty.SelectedIndex > -1) 
{
    Hide();
    //Main Menu form closes where user selects difficulty
    new Game().Show();
    //Game form where user player actual game

    Form2.playerStudent.Difficulty = combo_difficulty.Text;


    //This is a test and it outputs the difficulty as ecpected
    MessageBox.Show(Form2.playerStudent.Difficulty);
}

这是显示我所指的属性的学生班。

public class Student : Player
{
    private int _score;
    private string _difficulty;

    public Student(string username, string password, int score) : base(username, password) 
    {
        _score = Score;
    }

    public string Difficulty
    {
        get { return _difficulty; }
        set { _difficulty = value; }
    }

但是当我想在游戏形式中阅读所选择的难度时，不会返回任何值。我希望此消息显示用户在以前的表单中选择的难度。

public Game()
{
    InitializeComponent();          
    MessageBox.Show(Form2.playerStudent.Difficulty);
    //this message box is empty
    //other code...
}