private void mnuThongKeTonKho_Click(object sender, EventArgs e)
{
ThongKeTonKho thongKeTonKhoFrm = new ThongKeTonKho();
thongKeTonKhoFrm.MdiParent = this;
thongKeTonKhoFrm.Show();
}
void Load_ThongkeXuatnhapton()
{
ThongKeTonKho bll = new ThongKeTonKho();
DateTime firstDayOfMonth = new DateTime(dateTimePickerNLP.Value.Year, dateTimePickerNLP.Value.Month, 1);
DateTime lastMonth = firstDayOfMonth.AddDays(-1).Date;
DateTime currentTime = dateTimePickerNLP.Value.Date;
var data = bll.ThongKeXuatNhapTon(lastMonth, currentTime);
dtgvXuatNhapTon.DataSource = data;
}