private void Nhap_Hoa_Don_control_Load(object sender, EventArgs e)
{
DataTable _dshd = HoaDonBLL.LayDSHD();
dgvHoaDon.DataSource = _dshd;
List <String> dshh = HangHoaBLL.LayListHH();
comboBox2.DataSource = dshh;
comboBox2.DisplayMember = "MaHang";
comboBox2.SelectedIndex = -1;
DataTable listHTTT = HinhThucTTBLL.LayListHTTT();
comboBox1.DataSource = listHTTT;
comboBox1.DisplayMember = "TenHTTT";
comboBox1.ValueMember = "MaHTTT";
DataTable listDVMH = DVMHBLL.LayDSDVMH();
comboBoxDVM.Properties.DataSource = listDVMH;
comboBoxDVM.Properties.DisplayMember = "TenDonViMuaHang";
}