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