Cant get 2 datatable values in a crystal report

Im using 2 datatables to get the values in my report with 2 sub reports

by using this code i can get only the values in dti how can i get both please help..!

im using a web application this report is to get the totoal of sales and expense

protected void btnPrint_Click(object sender, EventArgs e)

{

DataTable dti = new DataTable();

DataTable dte = new DataTable();

try

{

InvoiceBLL invmbll = new InvoiceBLL();

if (txtFromDate.Text == "")

{

_fromDate = "1001-01-01";

}

else

{ _fromDate = DateTime.ParseExact(txtFromDate.Text, "dd/MM/yyyy", CultureInfo.InstalledUICulture).ToString("yyyy/MM/dd"); }

if (txtToDate.Text == "")

{

_toDate = "2100-12-31";

}

else

{ _toDate = DateTime.ParseExact(txtToDate.Text, "dd/MM/yyyy", CultureInfo.InstalledUICulture).ToString("yyyy/MM/dd"); }

dti = invmbll.GetInvoiceDaily(_fromDate,_toDate);

dte = invmbll.GetInvoiceDailyExpense(_fromDate, _toDate);

dti.TableName = "DailyCashIncomeReport";

dte.TableName = "DailyCashExpenseRpt";

string ReportName = Server.MapPath("~/Report/DailySalesExpenseReport.rpt");

Session["DTbl"] = dti;

Session["DTbl"] = dte;

Session["ReportName"] = ReportName;

Page page = (Page)HttpContext.Current.Handler;

if (page == null)

{

throw new InvalidOperationException("Cannot redirect to new window outside Page context.");

}

string url = "~/ShowReport.aspx";

url = page.ResolveClientUrl(url);

string windowFeatures = "";

if (!String.IsNullOrEmpty(windowFeatures))

{

script = @"window.open(""{0}"", ""{1}"", ""{2}"");";

}

else

{

script = @"window.open(""{0}"", ""{1}"");";

}

script = String.Format(script, url, "_blank", windowFeatures);

ScriptManager.RegisterStartupScript(page, typeof(Page), "Redirect", script, true);

}

catch (Exception ex) { throw new Exception(ex.ToString()); }

}