public void loadData()
{
dataGridView1.DataSource = HangBUS.loadAllDataHang();
(dataGridView1.Columns["MaLoai"] as DataGridViewComboBoxColumn).DataSource = loaiHang;
(dataGridView1.Columns["MaLoai"] as DataGridViewComboBoxColumn).DisplayMember = "TenLoai";
(dataGridView1.Columns["MaLoai"] as DataGridViewComboBoxColumn).ValueMember = "MaLoai";
}