WpfExtensions | Useful WPF controls and tools

I am trying to learn dependency properties and attached properties, so please forgive me if you find no use in what I am trying to do.

I have a usual MVVM approach with a Window whose datacontext is set to a VM, and View which is a datatemplate containing a usercontrol targetting such VM.

I am trying to make the window container as dumb as possible, as such i'm trying to define some parameters that usually reside in the window XAML (e.g. the height) via the usercontrol using Attached Properties.

For that purpose I created the following class where I define the attached property:

I want to use the pinch gesture too zoom with the WPFExtensions.Controls.ZoomControl.

Based on this answer - i know how to detect the pinch gesture. I use it as member _detector. I use ZoomControl.ManipulationDelta to do the zoom.

So I thought i just take ManipulationDelta and Zoom like this:

I use MetroWindow class from Mahapps to show dialog window of some kind. My idea was to create auto resizable window, to fit it's content size