No valid report source is available error in crystal report

#Simple Solution ( although this code is a vb.net code ; but the idea is same and simple )

I have just Solved this problem using CrystalReportViewer **Navigate Event**

in View report Button i have saved report document in a session

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
       ' -- the ds is dataset variable containing data to be displayed in the report
        
        rptDoc.SetDataSource(ds)
        Session.Add("rptdoc", rptDoc)
        CrystalReportViewer1.ReportSource = rptDoc

        End Sub  

then in Navigate event of CrystalReportViewer i set the CrystalReportViewer data source to the Session

Protected Sub j(ByVal source As Object, ByVal e As CrystalDecisions.Web.NavigateEventArgs) Handles CrystalReportViewer1.Navigate

    rpt.SetDataSource(ds)
    CrystalReportViewer1.ReportSource = session("rptdoc")

End Sub

So each time before you navigate to another page in the report , CrystalReportViewer data source is set to the report document saved in the session.