Animating Height Of box view

This is my first foray into Animation for my Forms App. I have seen loads of examples for scaling box views, but thee all seem to scale both heigh and width. I want to scale just the height with animation>

I have tried :

                        bar.Animate("HeightRequest", animation:new  Animation( callback:(double d) => { bar.HeightRequest = d; }, start:0, end:currentBarHeight, easing:Easing.SpringIn), length: 1000);

but this seems to do nothing. Are there any examples out there of scaling just the height of a box view??

Thanks Ash..