Can you use a Xamarin.Forms DialogAlert in the platform-specific project?

Hi,
I created a project which has a lot of shared code and some platform-specific code for Droid and iOS.
I call the specific code for iOS to perform a specific task (call a number, for instance).
Is it possible, in this platform-specific code, to call any Xamarin.Forms UI code?
I am trying to display an alert box in iOS with DisplayAlert but the compiler tells me it doesn't know what it is.
The only way is using the usual UIAlertView.
Any thoughts?
Thanks in advance.