Print Only Grid View in ASP.net

ASP.net How to Print Only GridView

<div id="gridviewDiv">

   <asp:GridView ID="gridViewToPrint" runat="server" 

                  DataSourceID="SqlDataSource1">

     <Columns>

    <asp:BoundField DataField="CategoryID" 

                    HeaderText="CategoryID"/>

    <asp:BoundField DataField="CategoryName" 

                    HeaderText="CategoryName"/>

    </Columns>

    </asp:GridView>

   </div>

   <asp:Button ID="btnPrint" runat="server" 

               Text="Print GridView Data"/>

protected void Page_Load(object sender, EventArgs e)
    {
        string printScript =
        @"function PrintGridView()
         {
            var gridInsideDiv = document.getElementById('gridviewDiv');
            var printWindow = window.open('gridview.htm','PrintWindow','letf=0,top=0,width=150,height=300,toolbar=1,scrollbars=1,status=1');
            printWindow.document.write(gridInsideDiv.innerHTML);
            printWindow.document.close();
            printWindow.focus();
            printWindow.print();
            printWindow.close();}";
        this.ClientScript.RegisterStartupScript(Page.GetType(), "PrintGridView", printScript.ToString(), true);
        btnPrint.Attributes.Add("onclick", "PrintGridView();");       
    }