xaml - Wpf disable repeatbuttons when scrolled to top/bottom -

i'm making touchscreen interface uses listbox.
have button above , below listbox page up/down.

i'm trying when scrolled way pageup button gets disabled.
, when scrolled way down pagedown button gets disabled too.

here's code in styles.xaml listbox

<style x:key="{x:type listbox}" targettype="{x:type listbox}">       <setter property="template">           <setter.value>               <controltemplate x:key="{x:type listbox}" targettype="{x:type listbox}">                   <dockpanel>                       <repeatbutton x:name="lineupbutton" dockpanel.dock="top"                           horizontalalignment="stretch"                            height="50"                           content="/\"                           command="{x:static scrollbar.pageupcommand}"                           commandtarget="{binding elementname=scrollviewer}" />                         <repeatbutton x:name="linedownbutton" dockpanel.dock="bottom"                           horizontalalignment="stretch"                           height="50"                           content="\/"                           command="{x:static scrollbar.pagedowncommand}"                           commandtarget="{binding elementname=scrollviewer}" />                       <border borderthickness="1" borderbrush="gray" background="white">                             <scrollviewer x:name="scrollviewer">                               <itemspresenter/>                           </scrollviewer>                       </border>                   </dockpanel>               </controltemplate>           </setter.value>       </setter>       <setter property="scrollviewer.horizontalscrollbarvisibility" value="hidden"/>       <setter property="scrollviewer.verticalscrollbarvisibility" value="hidden"/>       <setter property="focusvisualstyle" value="{x:null}" />   </style>  

and here's instantiate listbox

<listbox selecteditem="{binding selectedcan}" itemssource="{binding path=selectedkioskcashcans}">       <listbox.itemtemplate>           <datatemplate>               <contentpresenter content="{binding image}" maxwidth="75" />           </datatemplate>        </listbox.itemtemplate>        <listbox.itemspanel>            <itemspaneltemplate>                <virtualizingstackpanel orientation="vertical"/>            </itemspaneltemplate>        </listbox.itemspanel>   </listbox>  

i searched around yesterday no luck.
i'm hoping able in xaml.

i'm using images buttons took them out readability above,
like...

<repeatbutton x:name="lineupbutton" dockpanel.dock="top" horizontalalignment="stretch"      height="50"           command="{x:static scrollbar.pageupcommand}"           commandtarget="{binding elementname=scrollviewer}">         <repeatbutton.template>              <controltemplate targettype="{x:type repeatbutton}">                  <grid>                      <image name="normal" source="/images/up.png"/>                      <image name="pressed" source="/images/up.png" visibility="hidden"/>                  </grid>                  <controltemplate.triggers>                       <trigger property="ispressed" value="true">                           <setter targetname="normal" property="visibility" value="hidden"/>                           <setter targetname="pressed" property="visibility" value="visible"/>                       </trigger>                   </controltemplate.triggers>              </controltemplate>         </repeatbutton.template>    </repeatbutton> 

just use canexecute method of pageupcommand that. return false if no pages left , button become disabled automatically.

edit:

i have created simple attached behavior can used fix problem. set following attached property on scrollviewer:

<scrollviewer x:name="scrollviewer"               z:scrollbarcommandscanexecutefixbehavior.isenabled="true">        <itemspresenter/>   </scrollviewer>  

and here source code of behavior:

public static class scrollbarcommandscanexecutefixbehavior {     #region nested types      public class commandcanexecutemonitor<t> t : uielement     {         protected t target { get; private set; }          protected commandcanexecutemonitor(t target, routedcommand command)         {             target = target;              var binding = new commandbinding(command);              binding.canexecute += oncanexecute;              target.commandbindings.add(binding);         }          protected virtual void oncanexecute(object sender, canexecuteroutedeventargs e)         {          }     }      public class pageupcanexecutemonitor : commandcanexecutemonitor<scrollviewer>     {         public pageupcanexecutemonitor(scrollviewer scrollviewer)             : base(scrollviewer, scrollbar.pageupcommand)         {         }          protected override void oncanexecute(object sender, canexecuteroutedeventargs e)         {             if (e.handled)             {                 return;             }              if (equals(target.verticaloffset, 0.0))             {                 e.canexecute = false;                 e.handled = true;             }         }     }      public class pagedowncanexecutemonitor : commandcanexecutemonitor<scrollviewer>     {         public pagedowncanexecutemonitor(scrollviewer scrollviewer)             : base(scrollviewer, scrollbar.pagedowncommand)         {         }          protected override void oncanexecute(object sender, canexecuteroutedeventargs e)         {             if (e.handled)             {                 return;             }              if (equals(target.verticaloffset, target.scrollableheight))             {                 e.canexecute = false;                 e.handled = true;             }         }     }      #endregion      #region isenabled attached property      public static bool getisenabled(dependencyobject obj)     {         return (bool) obj.getvalue(isenabledproperty);     }      public static void setisenabled(dependencyobject obj, bool value)     {         obj.setvalue(isenabledproperty, value);     }      public static readonly dependencyproperty isenabledproperty =         dependencyproperty.registerattached("isenabled", typeof (bool), typeof (scrollbarcommandscanexecutefixbehavior), new propertymetadata(false, onisenabledchanged));      private static void onisenabledchanged(dependencyobject d, dependencypropertychangedeventargs e)     {         if ((bool) e.newvalue)         {             var scrollviewer = d scrollviewer;              if (scrollviewer != null)             {                 onattached(scrollviewer);             }             else             {                 throw new notsupportedexception("this behavior supports scrollviewer instances.");             }         }     }      private static void onattached(scrollviewer target)     {         setpageupcanexecutemonitor(target, new pageupcanexecutemonitor(target));         setpagedowncanexecutemonitor(target, new pagedowncanexecutemonitor(target));     }      #endregion      #region pageupcanexecutemonitor attached property      private static void setpageupcanexecutemonitor(dependencyobject obj, pageupcanexecutemonitor value)     {         obj.setvalue(pageupcanexecutemonitorproperty, value);     }      private static readonly dependencyproperty pageupcanexecutemonitorproperty =         dependencyproperty.registerattached("pageupcanexecutemonitor", typeof (pageupcanexecutemonitor), typeof (scrollbarcommandscanexecutefixbehavior), new propertymetadata(null));      #endregion      #region pagedowncanexecutemonitor attached property      private static void setpagedowncanexecutemonitor(dependencyobject obj, pagedowncanexecutemonitor value)     {         obj.setvalue(pagedowncanexecutemonitorproperty, value);     }      private static readonly dependencyproperty pagedowncanexecutemonitorproperty =         dependencyproperty.registerattached("pagedowncanexecutemonitor", typeof (pagedowncanexecutemonitor), typeof (scrollbarcommandscanexecutefixbehavior), new propertymetadata(null));      #endregion } 

the basic idea add commandbinding scrollviewer each of commands , subscribe canexecute event on bindings. in event handler check current position of scroll , set e.canexecute property accordingly.