Quick example of a bindable picker in Xamarin.Forms
Note that this example will only work with Xamarin.Forms 2.3.4 and above. As of November 29, 2.3.4 is not on NuGet yet - so you will have to build from source.
I have the NuGet setup to pull Forms 2.3.3 ... so there will be compilation errors. But the point of having this out there is for you to see the code and when 2.3.4 is released update the NuGet to point to that.
Accompanying blog post can be found here: https://codemilltech.com/xamarin-forms-bindable-picker/