键盘事件只能输入数字和FileUpload选中预览图片

 <script language="javascript" type="text/javascript" >
       function pho()
         {
         if(event.keyCode<45 || event.keyCode>57)
            {
                event.keyCode=0;
            }
         }
       function showimg()
         {
            document.getElementById ("Image1").src=document.getElementById ("FileUpload1").value;
         }
 </script>

 <asp:TextBox ID="TextBox3" runat="server" onKeypress="pho()"></asp:TextBox>

 <asp:Image ID="Image1" runat="server" Height="81px" Width="119px" />
 <asp:FileUpload ID="FileUpload1" runat="server" οnchange="showimg()" Width="157px" />