Ok, I'm in the right direction.
I have 5 bar "button" that are panels containing two label. The top label is a material icon and the bottom label is text.
Now when the device is rotated in landscape, I have to rearrange the size of the panels and the position of the labels (side by side and not one under the other).
I'm managing this in the Page_Resize event.
This works perfect in the test app I attach here.
but when I trasnfer the code inside my real app, the behaviour is wrong.
If I run step by step in the resize event, I see the five elements are rearranged as I want with the labels side by side, but when the event is terminated the elements turn back to the original format (and the bottom label is only partially visible because the height of the BottomBar is lower when the device is in landscape)
I can't understand where is the difference from the test app and the real app.
I attach the zip. May I know at least if the code is correct ?