Help with accessing a globe variable on a form from other form problem, thank you

[lwong]

Hi,
I am sorry for poor programming skill.
I have a form. Inside, I declared a global variable loginflag, the initial value is false, when users login, the value becomes true.But when I accessed this variable in other form, it always shows false.

//declare 
public bool loginflag=false;

//update the loginflag to true
 private void btOK_Click(object sender, EventArgs e)
        {
            if (txtusers.Text == "")
               .......
                    
            else
             {
                      
            LoginFlag = true;
            cSingleton.Instance.Main.Show();
                 
             } 
        }

//create singleton for accessing between forms 
  public sealed class cSingleton
    {
        FMain _Main;
        FLogin _login;


        public cSingleton() 
        {
         _Main = new FMain();
      
        _login = new FLogin();

        }
        static readonly cSingleton _Instance  = new cSingleton();
       
        public static cSingleton Instance
        {
            get { return _Instance; }
        }
        public FMain Main
        {
            get { return _Main; }
        }
   

        public FLogin Login
        {
            get { return _login; }
        }
 
    }

//access loginflag from other form
              else
                {
                    while (OpenComPort())
                    {
                        if (dr == DialogResult.Cancel)
                        {
                            dr = DialogResult.Retry;
                            
                            return;
                     }
                       
                        MessageBox.Show(cSingleton.Instance.Login.LoginFlag .ToString());//always false. problem here
}

What causes this? Thank you.

[TheGreatCthulhu]

I presume that the first two code blocks are from FLogin class?
Show us the code for the LoginFlag property, and make sure to denote the containing class if you're posting code from multiple classes. Also, I'd like to see what is passed to Application.Run() method in Program.cs.
BTW, the constructor of your singleton mediator class should be private, otherwise, you'll be able to construct more than one "singleton".

The best I can think of without seeing the declaration of LoginFlag and the call to Application.Run(), is that either there's something wrong with the LoginFlag property, or that the FLogin object where you set the login flag is not the same as the FLogin object held inside the singleton instance (meaning that you have a duplicate copy of your login form, which is never shown).

[lwong]

Thank you very much for replying.
Yes, the first two codes are from Flogin.cs
The LoginFlag property and Application run as below for Flogin.cs.

    public FLogin()
        {
            InitializeComponent();
        }

        public bool LoginFlag
        {
            get { return loginflag; }
            set { loginflag = value; }
        }

        [STAThread]
        static void Main()
        {
            Application.Run(new FLogin());
         }

Sorry, if you need further information, please let me know.
Thank you again.

[TheGreatCthulhu]

Yeah, the Form passed to Application.Run() and the one in the cSingleton are two separate instances.

Just replace the line

Application.Run(new FLogin());

with:

Application.Run(cSingleton.Instance.Login);

[lwong]

Thank you very much
TheGreatCthulhu
I can get the correct value now.
Thank you again.