我的猜测是，您 AnotherControl 未明确给出 Height 。不幸的是，在WinRT中（与WPF不同，但与Silverlight不同）， ActualWidth 和 ActualHeight 是所谓的计算属性。这意味着更改事件的属性不会在内部引起改变。因此，绑定到它们是不可靠的，正如你所注意到的，它不会奏效。

旁注：它可能会不时工作，但这纯粹是因为获取调用绑定框架的时间到 ActualHeight 。

因此，您只能使用XAML 不能进行操作。您必须在代码隐藏中处理 ActualControl.SizeChanged 事件，并将 Height 设置为 AnotherControl.ActualHeight 显式。

I'm trying to have 2 controls have the same height. Can I do it with XAML only?

If I did something like <Canvas Height="{Binding Height, ElementName=AnotherControl}" /> it doesn't actually do anything and the height goes to zero. The Output panel doesn't complain about any binding errors so AnotherControl.Height really exists. I tried binding to ActualHeight but it doesn't do anything either.

Anything else I missed?

My guess is that you AnotherControl is not explicitly given a Height. Unfortunately, in WinRT (unlike WPF, but the same as Silverlight), ActualWidth and ActualHeight are what are known as "calculated properties". This means that a property changed event doesn't internally get raised when they change. As a result, binding to them is not reliable, and as you've noticed, it wouldn't quite work.

Side note: it may work from time to time, but that is purely because of the timing of the get call the binding framework makes to ActualHeight.

So as it stands, you cannot do it with XAML only. You have to handle the ActualControl.SizeChanged event in code-behind, and set the Height to AnotherControl.ActualHeight explicitly.