xaml - WPF MediaElement restart itself? -

i have xaml form contains (i simplified code keep transparent):

<grid>     <textblock grid.row="0"                fontsize="20"                foreground="yellow"                text="{binding errormessage}"/>     ... others controls ...      <mediaelement x:name="mediaplayer"                       grid.row="0"                       grid.rowspan="5"                       grid.column="0"                       grid.columnspan="3"                       loaded="mediaplayer_loaded"                       loadedbehavior="manual"                       mediaended="mediaplayer_mediaended"                       source="{binding currentad.path}" /> </grid> 

code behind:

    private void mediaplayer_loaded(object sender, system.windows.routedeventargs e)     {         mediaplayer.play();     }      private void mediaplayer_mediaended(object sender, system.windows.routedeventargs e)     {         mediaplayer.position = new timespan(0, 0, 0, 0, 1);         mediaplayer.play();     } 

as can see mediaelement shows on fullscreen when currentad object not null , plays , starts again when finishes. viewmodel contains timer elapse every 10 seconds , set errormessage property , currentad property (but when changed, method refresh() - listing below).

method datacontext:

void refresh()     {         try         {             advertisment newad = advertismentmanager.getcurrentad();             if (!newad.equals(currentad))                 currentad = newad;             ....             errormessage = "";         }         catch(exception ex)         {             errormessage = ex.message;         } 

my problem every call of refresh method video player restarting itself. isn't caused change of binded currentad path. caused assign errormessage variable. didn't find similar question on web , think it's strange behavior. ideas?