Printing GridView placed inside UpdatePanel in ASP.Net

This way

HTML

 <asp:ScriptManager runat="server">
        </asp:ScriptManager>
        <asp:UpdatePanel ID="upPrint" runat="server">
            <ContentTemplate>
                <asp:GridView ID="Gridview2" runat="server">
                    <Columns>
                        <asp:BoundField DataField="FileId" HeaderText="Name" />
                        <asp:BoundField DataField="Name" HeaderText="Name" />
                        <asp:BoundField DataField="Number" HeaderText="Number" />
                        <asp:BoundField DataField="Email" HeaderText="Email" />
                        <asp:BoundField DataField="Date" HeaderText="Date" />
                        <asp:BoundField DataField="Message" HeaderText="Message" />
                    </Columns>
                </asp:GridView>
                <asp:Button ID="btnPrintGrid" runat="server" OnClick="PrintAllPage" Text="Print" />
            </ContentTemplate>
        </asp:UpdatePanel>

Code

 protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            this.PopulateGrid2();
        }
    }

    private void PopulateGrid2()
    {
        DataTable dt2 = new DataTable();
        dt2.Columns.AddRange(new DataColumn[6]{  
                            new DataColumn("FileId", typeof(int)),
                            new DataColumn("Name", typeof(string)),
                            new DataColumn("Number", typeof(int)),
                            new DataColumn("Email", typeof(string)),
                            new DataColumn("Date", typeof(DateTime)),  
                            new DataColumn("Message", typeof(string))  });
        dt2.Rows.Add(1, "Jake", 12, "1@1.com", "2013/10/10", "Hello");
        dt2.Rows.Add(1, "Jhon", 32, "1@1.com", "2013/10/10", "Hello");
        dt2.Rows.Add(1, "Jake", 142, "1@1.com", "2013/10/10", "Hello");
        Gridview2.DataSource = dt2;
        Gridview2.DataBind();
    }

    protected void PrintAllPage(object sender, EventArgs e)
    {
        Gridview2.AllowPaging = false;
        this.PopulateGrid2();
        StringWriter sw = new StringWriter();
        HtmlTextWriter hw = new HtmlTextWriter(sw);
        Gridview2.RenderControl(hw);
        string gridHTML = sw.ToString().Replace("\"", "'")
            .Replace(System.Environment.NewLine, "");
        StringBuilder sb = new StringBuilder();
        sb.Append("<script type = 'text/javascript'>");
        sb.Append("window.onload = new function(){");
        sb.Append("var printWin = window.open('', '', 'left=0");
        sb.Append(",top=0,width=1000,height=600,status=0');");
        sb.Append("printWin.document.write(\"");
        sb.Append(gridHTML);
        sb.Append("\");");
        sb.Append("printWin.document.close();");
        sb.Append("printWin.focus();");
        sb.Append("printWin.print();");
        sb.Append("printWin.close();};");
        sb.Append("</script>");
        //ClientScript.RegisterStartupScript(this.GetType(), "GridPrint", sb.ToString());
        ScriptManager.RegisterStartupScript(Gridview2, this.GetType(), "GridPrint", sb.ToString(), false);
        Gridview2.AllowPaging = true;
        Gridview2.DataBind();
    }

    public override void VerifyRenderingInServerForm(Control control)
    {
        /* Verifies that the control is rendered */
    }