asp.net – 没有有效的报告来源 – 水晶报告

protected void Page_Load(object sender,EventArgs e)
{
       if (IsPostBack)
        {
            try
            {
                CrystalReportViewer1.ReportSource = (ReportDocument)Session["Report"];
                CrystalReportViewer1.RefreshReport();
                CrystalReportViewer1.DataBind();
            }
            catch (Exception ex)
            {

               // throw;
            } 
        }

    }
    protected void CrystalReportViewer1_PreRender(object sender,EventArgs e)
    {

    }
    protected void btnPrint_Click(object sender,EventArgs e)
    {
        ReportDocument rptDoc = new ReportDocument();
        rptDoc.Load(Server.MapPath("ReportsBalanceReportNewBalanceReport.rpt"));
        rptDoc.SetDataSource(ReportData());
        Session["Report"] = rptDoc;
        CrystalReportViewer1.ReportSource = rptDoc;
        CrystalReportViewer1.RefreshReport();
        CrystalReportViewer1.DataBind();
    }
    public DataTable ReportData()
    {
        string ClassName = ddlClass.SelectedValue;
        string Division = ddlDivison.SelectedValue;
        string Subject = ddlSubjects.SelectedValue;
        DataTable ReportData = objRpt.getReportData(ClassName,Division,Subject);
        return ReportData;
    }