Xamarin.Android, Visual Studio - Designer doesn't work with v7 AppCompat library

I want to create an app with Material Design using Xamarin and Visual Studio. I want to achieve this using the v7 AppCompat library, so my app runs well on older devices.

I have an activity with a toolbar and a button.

But in the Visual Studio Designer the layout isn't as it's supposed to be(No Material theme and no Toolbar):

But the strange thing is that it runs properly on my phone(without any changes made):

How can I fix this?

Currently the Visual Studio Designer doesn't show Support Library elements.
You can use Xamarin Studio, which lately improved there Designer very much, and is easier to integrate with Visual Studio than Android Studio.
To download it go to http://download.xamarin.com/studio/Windows/XamarinStudio-6.0.2.73-0.msi (also available through your dashboard in www.xamarin.com under downloads, different versions).

EDIT: Currently you need to change the Cycle to beta (Help -> Check for Updates)