private void BtnExport_Click(object sender, EventArgs e) { ExportToExcel excel = new ExportToExcel(); string query = "SELECT * FROM dbo.CTHDBan"; System.Data.DataTable data = DataProvider.Instance.ExecuteQuery(query); excel.ExportCTHDBan(data, "Danh sach CTHDBan", "HÓA ĐƠN BÁN: " + maHDBan); }