Sir 
I have already added these Lines, but still error is there
my code is 
    Private Sub printform2()
      
        Dim connectionString, sql As String
            Dim connection As SqlConnection
            Dim reportdocument As New ReportDocument()
        reportdocument.Load(Server.MapPath("form2.rpt"))
        Using dsdeo As New dutylist()
            connectionString = ConfigurationManager.ConnectionStrings("accountsConnectionString").ToString
            connection = New SqlConnection(connectionString)
            '  Using con As New SqlConnection("Data Source=SureshDasari;Integrated Security=true;Initial Catalog=MySampleDB")
            connection.Open()
            'Dim cmd As New SqlCommand
            sql = "select a.centcode,a.name,a.duty,a.dutydays,b.centname as centname,b.students as students from centduty24 a left join centmast24 b on a.centcode=b.centcode where a.centcode=" & lblcentcode.Text & ""
            Using cmd As New SqlCommand(sql, connection)
                ''("select a.centcode,a.name,a.duty,a.dutydays,b.centname as centname,b.students as students from centduty24 a left join centmast24 b on a.centcode=b.centcode where a.centcode=" & lblcentcode.Text & "", connection)
                Using da As New SqlDataAdapter(cmd)
                    da.Fill(dsdeo, "centduty24")
                    connection.Close()
                    'End Using
                    Using examreport As New ReportDocument()
                        
                        examreport.Load(Server.MapPath("form2.rpt"))
                        examreport.SetDataSource(dsdeo.Tables("centduty24"))
                        examreport.SetDataSource(dsdeo)
                        examreport.ExportToHttpResponse(CrystalDecisions.[Shared].ExportFormatType.PortableDocFormat, Response, True, "form2")
                        examreport.Close()
                        examreport.Dispose()
                        GC.Collect()
                    End Using
                End Using
            End Using
        End Using
    End Sub
Sir, Pl examine the code and guide
Pl also advice how to get the file signed with DSC before downloading