private void button1_Click(object sender, EventArgs e)
{
XtraReport1 report = new XtraReport1();
//// Add bounded labels to the Detail band of the report.
report._bindData();
report._group();
report.DataSource = NhanVienPT.getAll();
ReportPrintTool printTool = new ReportPrintTool(report);
printTool.ShowRibbonPreview();
}