//--- OCULTAR E REVELAR O MENU PRINCIPAL
 public static void OcultaMenuPrincipal()
 {
     Main.frmPrincipal frm = Application.OpenForms.OfType <Main.frmPrincipal>().First();
     frm.mnuPrincipal.Visible = false;
     frm.pnlTop.BackColor     = Color.Gainsboro;
     frm.btnConfig.Enabled    = false;
 }
 //--- REVELA MENU PRINCIPAL
 public static void MostraMenuPrincipal()
 {
     if (Application.OpenForms.Count == 0)
     {
         return;
     }
     Main.frmPrincipal frm = Application.OpenForms.OfType <Main.frmPrincipal>().First();
     frm.mnuPrincipal.Visible = true;
     frm.mnuPrincipal.Enabled = true;
     frm.pnlTop.BackColor     = Color.SlateGray;
     frm.btnConfig.Enabled    = true;
 }