private void btnSearch_Click(object sender, EventArgs e) { FlashCard fl = ManageSystem.SearchFlashCardEng(txtSearching.Text); if (fl != null) { index = fl.IdCard; } else { fl = ManageSystem.SearchFlashCardVie(txtSearching.Text); if (fl != null) { index = fl.IdCard; } else { return; } } curFlashCard = ManageSystem.GetFlashCard(index); ChangeFlashCard(curFlashCard.Eng, curFlashCard.IdCard); }