How to set AbsoluteLayout.LayoutBounds OnPlatform in XAML with AutoSize?

I tried this one but it didn't work

<AbsoluteLayout.LayoutBounds>

   <OnPlatform x:TypeArguments="Rectangle" iOS="0, 1, AutoSize, AutoSize" Android="0, 1, AutoSize, AutoSize" /> 

</AbsoluteLayout.LayoutBounds>