Is There a Way to Remove the Delay between an Interspersed Login form and the Main form?

Question

Following the suggestion here to create my login form in the project's Main method like so:

[MTAThread]
static void Main()
{
    AppDomain.CurrentDomain.UnhandledException += Unhandled;

    frmLogin loginForm = new frmLogin();
    if (loginForm.ShowDialog() != DialogResult.OK)
    {
        // If they hit "Close" just use the default values for now (for testing)
        HHSConsts.userName = "duckbilled";
        HHSConsts.pwd = "platypus";
        HHSConsts.currentSiteNum = "Packers20Seahawks19";
    }
    else
    {
        HHSConsts.userName = loginForm.UserName;
        HHSConsts.pwd = loginForm.Password;
        HHSConsts.currentSiteNum = loginForm.SiteNumber;
    }
    loginForm.Dispose();

    Application.Run(new frmMain());
}

The login form has two buttons, "OK" and "Close":

private void buttonOK_Click(object sender, EventArgs e)
{
    HHSConsts.userName = textBoxUsername.Text.Trim();
    HHSConsts.pwd = textBoxPwd.Text.Trim();
    HHSConsts.currentSiteNum = listBoxSitesWithFetchedData.SelectedItem.ToString();
    // TODO: Prevent shutdown if "OK" is selected and there are any missing or bogus values?
    this.Close();
}

private void buttonClose_Click(object sender, EventArgs e)
{
    this.Close();
}

This works pretty fair, but there is a definite delay between the login form closing and the main form displaying. Is there a way to close this gap so that the interval is not so noticeable?

UPDATE

Replacing this:

Application.Run(new frmMain());

...with this:

Application.Run(new Form());

...in Program.cs results in the following:

Clicking the OK button on the login form: app closes (main form never displays)

Clicking the Close button on the login form: all the controls on the login form disappear, but the form stays up...?!?

Answer 1

Try pre-loading the main form with as much as you can:

[MTAThread]
static void Main()
{
  var mainForm = new frmMain();

  using(loginForm = new frmLogin())
  {
    if (loginForm.ShowDialog() != DialogResult.OK)
    {
      // If they hit "Close" just use the default values for now (for testing)
      HHSConsts.userName = "duckbilled";
      HHSConsts.pwd = "platypus";
      HHSConsts.currentSiteNum = "Packers20Seahawks19";
    }
    else
    {
      HHSConsts.userName = loginForm.UserName;
      HHSConsts.pwd = loginForm.Password;
      HHSConsts.currentSiteNum = loginForm.SiteNumber;
    }
  }

  mainForm.NotifyTheFormInstanceTheCredentialsHaveChangedIfItIsNotEventDrivenAlready();

  Application.Run(mainForm);
}