public void zoomToFitMapAnnotations()
        {
            if (map.Annotations.Length <= 0)
                return;

            var topLeftCoord = new CLLocationCoordinate2D(-90, 180);
            var bottomRightCoord = new CLLocationCoordinate2D(90, -180);

            foreach (var marker in map.Annotations)
            {
                topLeftCoord.Longitude = Math.Min(topLeftCoord.Longitude, marker.Coordinate.Longitude);
                topLeftCoord.Latitude = Math.Max(topLeftCoord.Latitude, marker.Coordinate.Latitude);

                bottomRightCoord.Longitude = Math.Max(bottomRightCoord.Longitude, marker.Coordinate.Longitude);
                bottomRightCoord.Latitude = Math.Min(bottomRightCoord.Latitude, marker.Coordinate.Latitude);

            }

            double delta = 1.4;
            MKCoordinateRegion region = new MKCoordinateRegion();
            region.Center.Latitude = topLeftCoord.Latitude - (topLeftCoord.Latitude - bottomRightCoord.Latitude)*0.5; //0.5
            region.Center.Longitude = topLeftCoord.Longitude + (bottomRightCoord.Longitude - topLeftCoord.Longitude)*0.5; //0.5
            region.Span.LatitudeDelta = Math.Abs((topLeftCoord.Latitude - bottomRightCoord.Latitude)* delta);
            region.Span.LongitudeDelta = Math.Abs((bottomRightCoord.Longitude - topLeftCoord.Longitude) * delta);

            region = map.RegionThatFits(region);
            map.SetRegion(region, true);
        }


        private void CenterMap(CLLocationCoordinate2D mapCenter)
        {
            InvokeOnMainThread(() =>
            {
                map.SetRegion(MKCoordinateRegion.FromDistance(mapCenter, 1000, 1000), true);
            });
        }