public static new DialogResult Show(Gravity gravitylevel, SetButton buttonsetup, string messaggio)
{
    MyMessageBox mymb = new MyMessageBox();
    mymb.mGravity = gravitylevel;
    mymb.mMessaggio = messaggio;
    mymb.listBtn.Add(btnCancel);
    mymb.listBtn.Add(btnNo);
    mymb.listBtn.Add(btnOK);
    mymb.listBtn.Add(btnYes);
    mymb.mButtonSetUp = buttonsetup; 
    return mymb.ShowDialog();
}