ASP. NET method for passing values between forms

Assume that there is an TextBox1 text box and an Open button on the ES0en.aspx page
Click Open button to pop up SubForm. aspx, SubForm. aspx page has TextBox1 text box and Close button
Click the Close button to close the SubForm.aspx page and display the value of the child page SubForm.aspx text box on the parent page ParentForm.aspx text box.
Parent window foreground code:

      <script type="text/javascript">
        function OpenSubForm(ret) {
            var strPath = "subForm.aspx"
            var nHeight = 500
            var nWidth = 500
            var feature
            feature = "Height= " + nHeight + ",Width=" + nWidth + ",top=30,Left=30";
            feature += ",dependent=yes,location=no,resizable=yes,scrollbars=yes,status=yes,toolbar=no;";
            window.open(strPath+"?Ret_Form=Form1&Ret_Value="+ret,'subForm',feature).focus();
            return false;
        }
    </script>

Parent form background code:

private void Page_Load(object sender, System.EventArgs e)
        {
            //  Early ペ � ジ を change す る ユ � ザ �   コ � ド を こ こ に � into し ま す 
            this.Button1.Attributes.Add("onClick","return OpenSubForm('TextBox1');");
        }

Subform background code:

        private void Button1_Click(object sender, System.EventArgs e)
        {
            string strScript =string.Empty;
            string strRetForm = String.Empty;
            string strRetValue=String.Empty;
            strRetForm=Request.Params["Ret_Form"];
            strRetValue=Request.Params["Ret_Value"];
            if (strRetForm == string.Empty)
            {
                strRetForm= "document.forms[0]";
            }
            strScript = "<script language=javascript>";
            strScript += "window.opener." + strRetForm;
            strScript += "." + strRetValue + ".value='" + this.TextBox1.Text.Trim() + "';";
            strScript += "window.close();";
            strScript += "</script>";
            Response.Write(strScript);
        }