title: MultiHandleSliderExtender and postback javascript issues
body: <p>I am trying t use the multihandlesliderextender (from the Ajax Toolkit) to make a filter option on the price in a webshop. When a new price is selected, it has to reload everything (and do a lot of behind the scenes code).</p>
  
  <p>I've used this article here <a href="http://forums.asp.net/p/1397694/3022998.aspx" rel="nofollow">http://forums.asp.net/p/1397694/3022998.aspx</a> as inspiration, and the primary idea is to use JavaScript to make the postback.</p>
  
  <p>I have the following error when running my page: <em>"Microsoft JScript runtime error: Unable to set value of the property 'Handle': object is null or undefined"</em>. </p>
  
  <p>I guess it's because the JavaScript can't find the control, but I don't get why it doens't work as I use ClientIdMode to make sure ID should match (and looking in the generated HTML it should work).</p>
  
  <p>Thanks!</p>
  
  <p>I've the following markup:</p>
  
  <pre><code> &lt;asp:TextBox ID="txtSlider" runat="server" AutoPostBack="true" &gt;&lt;/asp:TextBox&gt;
          &lt;asp:MultiHandleSliderExtender ID="MultiHandleSliderExtender1" BehaviorID="MultiHandleSliderExtender1"
              runat="server" TargetControlID="txtSlider" Length="120" TooltipText="{0}" OnClientDragEnd="ValueChangedHandler"&gt;
          &lt;MultiHandleSliderTargets&gt;
                  &lt;asp:MultiHandleSliderTarget ControlID="LeftHandle" /&gt;
  &lt;asp:MultiHandleSliderTarget ControlID="RightHandle" /&gt;
  
              &lt;/MultiHandleSliderTargets&gt;
  
          &lt;/asp:MultiHandleSliderExtender&gt;
  
          &lt;br/&gt;&lt;br/&gt;
              &lt;asp:TextBox ID="LeftHandle" runat="server" ClientIDMode="Static"&gt;&lt;/asp:TextBox&gt;
              &lt;asp:HiddenField ID="HiddenField1" runat="server" ClientIDMode="Static" /&gt;
  
  
  &lt;asp:Label ID="RightHandle" runat="server" ClientIDMode="Static"&gt;&lt;/asp:Label&gt;
   &lt;asp:HiddenField ID="HiddenField2" runat="server" ClientIDMode="Static" /&gt;
  
  
          &lt;asp:Button ID="Button1" runat="server" Text="Button" 
      Style="display: none" onclick="Button1_Click" /&gt;
          &lt;asp:Label ID="Label1" runat="server" Text=""&gt;&lt;/asp:Label&gt;
  </code></pre>
  
  <p>And in my header the following JavaScript:</p>
  
  <pre><code> &lt;script type="text/javascript"&gt;
  
       function ValueChangedHandler(sender, args) {
           $get("HiddenField1").value = $get("LeftHandle").value;
           $get("HiddenField2").value = $get("RightHandle").value;
           __doPostBack("Button1", "Click");
       }
  
  &lt;/script&gt;
  </code></pre>