missing parameter values error while click on print and export button of crystal report toolbar

I am binding reports on button click of web page.

protected void btnATreport_Click(object sender, EventArgs e)
{
ReportDocument reportdocument = new ReportDocument();
reportdocument.Load(Server.MapPath("CrpATReport.rpt").Replace("Content Pages\\CrpATReport.rpt", "Reports\\CrpATReport.rpt"));
reportdocument.DataSourceConnections[0].SetLogon("sa", "******");

getreport();//in this method fetching data conditionwise
}

getting error missing parameter vlaues..