How can I close a login form and show the main for

Question

I have two forms in my project (Login and Main).

What I'm trying to accoomplish is, if the login is successful, I must show the Main form and close the Login form.

I have this method in Login form that closes the Login form when the login is successful. But the Main form doesn't show.

public void ShowMain()
{
    if(auth()) // a method that returns true when the user exists.
    {             
        var main = new Main();
        main.Show();
        this.Close();
    }
    else
    {
        MessageBox.Show("Invalid login details.");
    }         
}

I tried hiding the Login form if the login process is successful. But it bothers me because I know while my program is running the login form is still there too, it should be closed right?

What should be the right approach for this? Thanks...

Answer 1

I think a much better method is to do this in the Program.cs file where you usually have Application.Run(form1), in this way you get a cleaner approach, Login form does not need to be coupled to Main form, you simply show the login and if it returns true you display the main form otherwise the error.

Answer 2

Try this:

public void ShowMain()
    {
        if(auth()) // a method that returns true when the user exists.
        { 
            this.Close();
            System.Threading.Thread t = new System.Threading.Thread(new System.Threading.ThreadStart(Main));
            t.Start();
        }
        else
        {
            MessageBox.Show("Invalid login details.");
        }         
    }
   [STAThread]
   public void Main()
   {
      Application.EnableVisualStyles();
      Application.SetCompatibleTextRenderingDefault(false);
      Application.Run(new Main());

   }

You must call the new form in a diferent thread apartment, if I not wrong, because of the call system of windows' API and COM interfaces.

One advice: this system is high insecure, because you can change the if condition (in MSIL) and it's "a children game" to pass out your security. You need a stronger system to secure your software like obfuscate or remote login or something like this.

Hope this helps.

Answer 3

static class Program
{
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Login();
    } 

    private static bool logOut;

    private static void Login()
    {
        LoginForm login = new LoginForm();
        MainForm main = new MainForm();
        main.FormClosed += new FormClosedEventHandler(main_FormClosed);
        if (login.ShowDialog(main) == DialogResult.OK)
        {
            Application.Run(main);
            if (logOut)
                Login();
        }
        else
            Application.Exit();
    }

    static void main_FormClosed(object sender, FormClosedEventArgs e)
    {
        logOut= (sender as MainForm).logOut;
    }
}

public partial class MainForm : Form
{
    private void btnLogout_ItemClick(object sender, ItemClickEventArgs e)
    {
        //timer1.Stop();
        this.logOut= true;
        this.Close();
    }
}

Answer 4

public void ShowMain()
  {
       if(auth()) // a method that returns true when the user exists.
       {        
         this.Hide();
         var main = new Main();
         main.Show();
       }
      else
       {
              MessageBox.Show("Invalid login details.");
        }         
   }

Answer 5

Here's a simple solution, your problem is that your whole application closes when your login form closes right? If so, then go to your projects properties and on the Application Tab change the shutdown mode to "When last form closes" that way you can use Me.close without closing the whole program

Answer 6

try this

 private void cmdLogin_Click(object sender, EventArgs e)
    {
        if (txtUserName.Text == "admin" || txtPassword.Text == "1")
        {

            FrmMDI mdi = new FrmMDI();
            mdi.Show();
            this.Hide();
        }
        else {

            MessageBox.Show("Incorrect Credentials", "Library Management System", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
        }
    }

and when you exit the Application you can use

 Application.Exit();