There are two typical modes of operation for a messenger application:
Use only the contacts on your device
Use only the contacts on the service being used
The reasons for this are never clear, and with the exception of privacy concerns, there really should be no reason why you cannot have access to both.
As far as we're concerned, we have to consider that we have to use something very platform-specific in terms of the address book, and for social media, we need to use various web services as well as some form of an authenticator system.
Xamarin does have a number of components available, which will help with most aspects, and we can certainly make use of them. There are also the likes of Xamarin.Forms.Labs that will help. There is little point in reinventing the wheel, so I will show you how to use these components as well. Xamarin.Forms.Labs is an extension library designed to fill the gaps not supported by Xamarin Forms. It is free and available via NuGet.
Irrespective of the...