The main form that will be displayed is the form that is set within the InitApplication() method where the call to "e.Forms.Add(GetType(MainFormType))" is made. The "MainFormType" is the System.Type of the main form that will be shown.
Within the ShowLoginAndInitMainForm() method, you won't have a reference to the main for, yet, but you can pass parameters to the main form's constructor through the event args of the method like this:
e.FormInitArgs.Add(Parameter1)e.FormInitArgs.Add(Parameter2)
Where Parameter1 and Parameter2 are passed to the main form's constructor like this:
public MyMainForm(string Parameter1, int Parameter2)
{
// save off the parameters into private fields
}