Print crystal report after executing my server side code?

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C#

Problem is to print crystal report using iFrame. In my following code I have called a Print() function in my server side code.

After clicking the button, it shows the error: Uncaught TypeError: Cannot read property 'contentWindow' of undefined(…)".

This Print() functions works perfectly for client side. How do I get solution now to call javascript function in my server side to print Crystal report?

What I have tried:

Server Side Code

protected void btnSave_Click(object sender, EventArgs e) {
  // any code here
  // load the database in crystal report
  // now I want to preview my print report with crystal viewer
  ScriptManager.RegisterStartupScript(this.Page, this.Page.GetType(), "Notification", "Print();", true);    
}

Client Side Code:

<div id="dvReport" class="col-md-12 col-sm-12 col-xs-12">
         <cr:crystalreportviewer id="CrystalReportViewer1" runat="server" width="600px" height="400px" autodatabind="true" bestfitpage="False" hastogglegrouptreebutton="False" hastoggleparameterpanelbutton="False" toolpanelview="None" enabledrilldown="False" printmode="Pdf">
</div>

<script>
        function Print() {
            var dvReceiptReport = document.getElementById("dvReport");
            var frame1 = dvReceiptReport.getElementsByTagName("iframe")[0];
                var frameDoc = frame1.contentWindow ? frame1.contentWindow : frame1.contentDocument.document ? frame1.contentDocument.document : frame1.contentDocument;
            frameDoc.print();
        }
    </script>