private void BtnExport_Click(object sender, EventArgs e) { ExportToExcel excel = new ExportToExcel(); string query = "SELECT * FROM dbo.HoaDonBan"; System.Data.DataTable data = DataProvider.Instance.ExecuteQuery(query); excel.ExportHoaDonBan(data, "Danh sach HDB", "DANH SÁCH HÓA ĐƠN BÁN"); }