Print only those rows of ASP.Net GridView which selected using CheckBox and print one row per page

    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns = "false">
        <Columns>
            <asp:TemplateField>
                <ItemTemplate>
                    <asp:CheckBox ID="CheckBox1" runat="server" />
                </ItemTemplate>
            </asp:TemplateField>
            <asp:BoundField DataField="Name" HeaderText="Name" />
            <asp:BoundField DataField="Age" HeaderText="Age" />
        </Columns>
    </asp:GridView>
    <asp:Button ID="btnPrint" runat="server" Text="Print" OnClick = "Print" />

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            DataTable dt = new DataTable();
            dt.Columns.AddRange(new DataColumn[2] { new DataColumn("Name"), new DataColumn("Age") });
            dt.Rows.Add("John", "12");
            dt.Rows.Add("Sam", "42");
            dt.Rows.Add("Mike", "31");
            dt.Rows.Add("Jerry", "19");
            dt.Rows.Add("Thomas", "77");
            GridView1.DataSource = dt;
            GridView1.DataBind();
        }
}
    public override void VerifyRenderingInServerForm(Control control)
    {
        /*Verifies that the control is rendered */
    }
    protected void Print(object sender, EventArgs e)
    {
        GridView1.Attributes["style"] = "border-collapse:separate";
        GridView1.HeaderRow.Visible = false;
        foreach (GridViewRow row in GridView1.Rows)
        {
            if (row.RowType == DataControlRowType.DataRow)
            {
                row.Cells[0].Visible = false;
                if ((row.FindControl("CheckBox1") as CheckBox).Checked)
                {
                    row.Attributes["style"] = "page-break-after:always;";
                }
                else
                {
                    row.Visible = false;
                }
            }
        }
        StringWriter sw = new StringWriter();
        HtmlTextWriter hw = new HtmlTextWriter(sw);
        GridView1.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(\"");
        string style = "<style type = 'text/css'>thead {display:table-header-group;} tfoot{display:table-footer-group;}</style>";
        sb.Append(style + gridHTML);
        sb.Append("\");");
        sb.Append("printWin.document.close();");
        sb.Append("printWin.focus();");
        sb.Append("printWin.print();");
        sb.Append("printWin.close();");
        sb.Append("};");
        sb.Append("</script>");
        ClientScript.RegisterStartupScript(this.GetType(), "GridPrint", sb.ToString());
        GridView1.DataBind();
    }