Example

Example.cs

//En AppDelegate.cs

public override bool ContinueUserActivity (UIApplication application, NSUserActivity userActivity, UIApplicationRestorationHandler completionHandler)
{
    string url = ""; //Sacas el ultimo segmento de userAcvitity.WebpageUrl y lo asignas aca
    if (!string.IsNullOrWhiteSpace (url)) {
      MessagingCenter.Send<NSUserActivitySearch.App, string> (Xamarin.Forms.Application.Current as NSUserActivitySearch.App, "ShowResetScreen", url);
    }
  return true;
}

//En App (proyecto core)
public App ()
{
  //Dentro del Initialize del App
  MessagingCenter.Subscribe <NSUserActivitySearch.App, string> (this, "ShowResetScreen", async (sender, arg) => {
    var resetHash = arg;
    await MainPage.Navigation.PushAsync (todoItemPage);
  });
}