iFrame from Vendor, browse from Main page to other page, dialog issue

Question

Hi All,

In an Iframe from other vendor, when navigating from Main page to other page or any modal like bootstrap modal,

it is displaying the dialog box "Do you want to leave the site", I tried to add the javascript code but still displaying this dialog box

 

<script type="text/javascript">
    window.onbeforeunload = function () {
      return null;  // return null to avoid pop up
    }
</script>

Dialog Box Issue:

In Index.cshtml

Response.Redirect("/ResponseResults"); -- to go to other page but this dialog issue occurred

Please kindly help how to fix this issue on ASP.NET CORE 3.1 Web Application and IIS 10. SSL already enabled/installed in IIS 10.

Thanks!

Rodel