wpf - Make a button "public" in xaml and c# -

i building mobile app using xamarin platform. in solution, there core project , platform specific projects, in case, .ios , .android. in core project have xaml layout, button element. my_app.core.homepage.xaml

<button x:name="loginicon"         image="key.png"         horizontaloptions="center"         verticaloptions="centerandexpand"         grid.row="9" grid.column="3" grid.columnspan="3" /> 

i have platform specific logic in projects, result of alter source of these buttons. e.g.

my_app.ios.customfile.cs:

my_app.homepage.loginicon.source = imagesource.fromfile("bluetoothg.png"); 

of course, button defined in xaml, loginicon isn't visible file, how can make xaml element public, can reference other projects in solution reference core files?

create property on page , return button:

public button publoginicon{ get{ return loginicon; } } 

but, must wrongly designed if must access controls on page, better approach have functionality in page public function, in case have no need access controls.