Question

I am using this function to close existing form and open a new form.

If there is no exixting form, it throws error.

Error :

Target : System.Object MarshaledInvoke(System.Windows.Forms.Control, System.Delegate, System.Object[], Boolean)

Message : Invoke or BeginInvoke cannot be called on a control until the window handle has been created.

Stack : at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)

SO need to check for any form open before closing the form to avoid the error. How?

    static public void NewMainForm(Form main, bool ClosePreviousMain)
    {
            if (main != null)
            {
                Global.ActiveForm = main.Text;
                if (ClosePreviousMain & MyContext.curMain != null)
                {
                    MyContext.curMain.FormClosed -= new FormClosedEventHandler(main_FormClosed);
                    //Need to check for any form active and then close the form.
                    MyContext.curMain.Invoke(new Action(MyContext.curMain.Dispose));
                }
                MyContext.curMain = main;
                MyContext.curMain.FormClosed += new FormClosedEventHandler(main_FormClosed);
                MyContext.curMain.ShowDialog();
            }
    }

Answer 1

You can use the Application.OpenForms collection.