public void loadData() { dataGridView1.DataSource = LopBUS.loadAllDataLop(); (dataGridView1.Columns["MaKhoa"] as DataGridViewComboBoxColumn).DataSource = khoa; (dataGridView1.Columns["MaKhoa"] as DataGridViewComboBoxColumn).DisplayMember = "TenKhoa"; (dataGridView1.Columns["MaKhoa"] as DataGridViewComboBoxColumn).ValueMember = "MaKhoa"; }