Set rectangle's values to AutoSize in XAML?

Hello,

How do I set rectangle values to Auto in XAML?

Here's an example of what I want to achieve in XAML, the shorter syntax I can get the better.

var label = new Label();
AbsoluteLayout.SetLayoutBounds(label, new Rectangle(Point.Zero, new Size(AbsoluteLayout.AutoSize, AbsoluteLayout.AutoSize)));

XAML:

<!-- Doesn't compile -->
<Label AbsoluteLayout.LayoutBounds="0,0,Auto,Auto" />