A square FrameworkElement in XAML fitting/filling its parent for Windows Store 8 or Windows Phone 8 -

i'd have frameworkelement in xaml equal width , height, fitting (or filling) parent, without hardcoding width , height specific values, both windows store 8 , windows phone 8 (not same solution).

for purpose of example, i'll use <image/>, frameworkelement.

i've attempted following, make frameworkelement square based on parent's width. wasn't able make square based on "minimal" (or maximal) value between parent's height , width.

<grid x:name="layoutroot">     <image         height="{binding actualwidth, elementname=layoutroot, mode=oneway}"         horizontalalignment="stretch"         /> </grid> 

i've attempted following, said scale , doesn't size frameworkelement. height , width still "1":

<viewbox stretch="uniform">     <image         height="1"         width="1"         /> </viewbox> 

i've heard <multibinding/> (for windows store 8 only, not windows phone 8 sadly), wasn't able code square behavior.