Hi,
Try to show us the code causes that Error
You may miss something like this
>> Dim Reportpath AS String = "D:\Reports\"
ReportViewer1.LocalReport.ReportPath = Reportpath + "Report1.rdlc" <<
Or you may miss to link Report1.rdlc to the ReportViewer1 from the designer Or ..........
We need more details in order to get help here
Regards From Egypt