.net - How to bind width of child element to width of parent element in WinRT -

i have progressbar in stackpanel. want progressbar have size of stackpanel or bit smaller.

i tried width="{binding actualwidth, elementname=parentelementname}" doesn't work in winrt

sample code

<stackpanel grid.row="1" margin="120,15,0,0">     <progressbar x:name="progressbar1"               value="{binding progresspercent}"                horizontalalignment="left"               isindeterminate="false"               maximum="100"               height="10"/> </stackpanel> 

you need provide path in binding.

width="{binding elementname=parentelementname, path=actualwidth}" 

see if works.