C# Windows Phone 8.1: ListView selected state not working as expected -

i have windows phone 8.1 (wp 8.1) listview. itemssource of listview observablecollection<item>, selectedvalue binds property selecteditem. see code snipped below.

        <listview             selectedvalue="{binding selecteditem, mode=twoway}"             itemssource="{binding items}">             <listview.itemcontainerstyle>                 <style targettype="listviewitem">                     <setter property="horizontalcontentalignment" value="stretch" />                     <setter property="foreground" value="#777" />                     <setter property="template">                         <setter.value>                             <controltemplate targettype="listviewitem">                                 <grid>                                     <visualstatemanager.visualstategroups>                                         <visualstategroup x:name="commonstates">                                             <visualstate x:name="normal"/>                                         </visualstategroup>                                         <visualstategroup x:name="selectionstates">                                             <visualstate x:name="unselected">                                                 <storyboard>                                                     <coloranimation duration="0" storyboard.targetname="myback" storyboard.targetproperty="(border.background).(solidcolorbrush.color)" to="transparent"/>                                                 </storyboard>                                             </visualstate>                                             <visualstate x:name="selected">                                                 <storyboard>                                                     <coloranimation duration="0" storyboard.targetname="myback" storyboard.targetproperty="(border.background).(solidcolorbrush.color)" to="#ff5b318f"/>                                                 </storyboard>                                             </visualstate>                                             <visualstate x:name="selectedunfocused">                                                 <storyboard>                                                     <coloranimation duration="0" storyboard.targetname="myback" storyboard.targetproperty="(border.background).(solidcolorbrush.color)" to="#ff5b318f"/>                                                 </storyboard>                                             </visualstate>                                         </visualstategroup>                                     </visualstatemanager.visualstategroups>                                     <border x:name="myback" background="transparent">                                         <contentpresenter content="{templatebinding content}" contenttemplate="{templatebinding contenttemplate}"/>                                     </border>                                 </grid>                             </controltemplate>                         </setter.value>                     </setter>                 </style>             </listview.itemcontainerstyle>             <listview.itemtemplate>                 <datatemplate>                     <border                         margin="15,0,0,0"                         borderthickness="0,0,0,1"                         borderbrush="#979797">                         <grid margin="-15,0,0,0" horizontalalignment="stretch" verticalalignment="stretch">                             <textblock padding="15" text="{binding description}" fontfamily="ms-appx:/fonts/lato-regular.ttf#lato" foreground="#777" fontsize="18" />                         </grid>                     </border>                 </datatemplate>             </listview.itemtemplate>         </listview> 

the selectedvalue binding working, background of (initial) selected item not change. changes after select item. have tried different visualstates without result.

why background not set on selectedvalue before select item?

thanks in advance,

michael