GoogleMapsSDKDemoController.cs

// Register an API key in your AppDelegate's FinsihedLaunching method:
// GMSServices.ProvideAPIKey ("Your API key.");

GMSMapView mapView;

public override void ViewDidLoad ()
{
    base.ViewDidLoad ();
    
    // Create the map view, framing Xamarin headquarters
    mapView = new GMSMapView {
        Camera = new GMSCamera (37.797865, -122.402526, 6)
    };
    
    // Add a marker for Sydney.
    var xamarinhq = new GMSMarkerOptions {
        Title = "Xamarin HQ",
        Snippet = "Where the magic happens.",
        Position = new CLLocationCoordinate2D (37.797865, -122.402526)
    };
    mapView.AddMarker (xamarinhq);
    
    // Set the map as our main view.
    View = mapView;
}

public override void ViewWillAppear (bool animated)
{
    base.ViewWillAppear (animated);
    mapView.StartRendering ();
}

public override void ViewWillDisappear (bool animated)
{
    base.ViewWillDisappear (animated);
    mapView.StopRendering ();
}