private void frmLapPhieuDat_Load(object sender, EventArgs e)
{
cboNCC.DataSource = NhaCungCapBUS.DanhSachNCC();
cboNCC.DisplayMember = "TenNhaCungCap";
cboNCC.ValueMember = "MaNhaCungCap";
dgvDanhSach.AllowUserToAddRows = false;
dtkNgayDat.Value = DateTime.Now;
dgvDanhSach.Rows.Clear();
}