How can I update asp.net main webform from child webform

I have two web forms in my asp.net project, in web form number 1 I have a button and I am writing this code to open web form number 2:

Response.Write("<script> var myWindow = window.open('DatePicker.aspx', '', 'width=400, height=500');</script>");

      

        
        
        
      

    

when web form number 2 is open, I want to close web form number 2, update web form number 1, for this reason I write this code on web form number 2:

<script type="text/javascript">
function RefreshParent() {
            if (window.opener != null && !window.opener.closed) {
                window.opener.location.reload();
                window.close(); // ADDED LINE
            }
        }
        window.onbeforeunload = RefreshParent;
    </script>

      

        
        
        
      

    

But web form number 1 won't reload, what's going on?