MultiHandleSlider: cant get even a simple working example to run

Hello,

Im using vs2012, all latest updates. Using the latest ajax control tookit 15.1.1.100

I am unable to get even a simple instance of this MultiHandleSlider to work and im tearing my hair out in frustration.

From this http://ajaxtoolkit.net/MultiHandleSlider/MultiHandleSlider.aspx I can see the control should work and its perfect for what I want.

I have created a simple new webforms basic solution, targeting .net 4.5.

Ive copy pasted basic samples from the web for this control. There are no errors when I run it. But the control only ever shows 1 single drag handle, even if I remove all MultiHandleSliderTarget it still shows 1 drag handle that drags ok.

If I try to access the list of MultiHandleSliderTarget in the code behind it shows the collection to be null.

   foreach (MultiHandleSliderTarget target in MultiHandleSliderExtender1.MultiHandleSliderTargets)
            target.ControlID = MultiHandleSliderExtender1.Parent.FindControl(target.ControlID).ClientID;

If I try to add them programmatically in code behind I get an error

Type 'AjaxControlToolkit.MultiHandleSliderTarget' in Assembly 'AjaxControlToolkit, Version=15.1.1.100, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e' is not marked as serializable

So im pretty much at my wits end on this, does this control even work in any way ?

Im desperate I need some help please.

None of the target controls are in an containers its just a simple webform where im trying to get this multihandle control running.

<cc1:MultiHandleSliderExtender ID="MultiHandleSliderExtender1"
                                    runat="server" ShowHandleDragStyle="false"
                                    BehaviorID="MultiHandleSliderExtender1" TargetControlID="txtSlider"
                                    Length="500" ShowInnerRail="false"
                                    EnableMouseWheel="true" Increment="1"
                                    RaiseChangeOnlyOnMouseUp="true" EnableRailClick="true"
                                    OnClientDragEnd="" OnClientDrag=""
                                    ShowHandleHoverStyle="true"
                                    Maximum="222" Minimum="1" BoundControlID ="txtSlider">
                                    <cc1:MultiHandleSliderTargets>
                                        <cc1:MultiHandleSliderTarget ControlID="lblStartRange" runat="server" />
                                        <cc1:MultiHandleSliderTarget ControlID="lblEndRange" runat="server" />
                                      
                                    </cc1:MultiHandleSliderTargets>
                                </cc1:MultiHandleSliderExtender>