private void LoadCanHo()
        {
            var danhSachCanho = context.layDanhSachCanHo();

            cboMaCanHo.Items.Clear();
            cboTang.Items.Clear();
            foreach (var ch in danhSachCanho)
            {
                cboMaCanHo.Items.Add(ch.ma.ToString().Trim());
            }
        }