Generally, this has been harder than it needs to be because there’s quite a lot of out of date information out there.

One thing that really threw me was trying to work with responsive layouts. I kept seeing this:

Parent.Width *  
    Switch(Parent.Size,  
        ScreenSize.Small, 0.5,  
        ScreenSize.Medium, 0.3,  
        0.25)

Well, Parent.Size just didn’t want to work for me. I did eventually find out why: Size is a property of Screen controls. So, if you have a Screen control called “Main” Main.Size will get what you want.

Obviously if you’re working with a control that has a Screen as a parent, Parent.Size will work. So, while Parent might be useful shorthand when you’re writing… it’s not when you’re learning.