public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();

            this.flexChart.ItemsSource = new LineMarkerViewModel().Items;
            initMarker();
        }
        StackLayout layout = new StackLayout();
        Label xLabel = new Label();
        IList<Label> yLabels = new List<Label>();
        private void initMarker()
        {
            xLabel.VerticalOptions = LayoutOptions.FillAndExpand;
            xLabel.HorizontalOptions = LayoutOptions.FillAndExpand;

            layout.Children.Add(xLabel);

            for (int index = 0; index < flexChart.Series.Count; index++)
            {
                var series = flexChart.Series[index];
                var fill = (int)((IChart)flexChart).GetColor(index);
                Label yLabel = new Label();
                yLabel.VerticalOptions = LayoutOptions.FillAndExpand;
                yLabel.HorizontalOptions = LayoutOptions.FillAndExpand;
                var bytes = BitConverter.GetBytes(fill);
                yLabel.TextColor = Color.FromRgba(bytes[2], bytes[1], bytes[0], bytes[3]);
                yLabels.Add(yLabel);
                layout.Children.Add(yLabel);
            }
            lineMarker.Content = layout;
        }
        private void OnLineMarkerPositionChanged(object sender, PositionChangedArgs e)
        {
            if (flexChart != null)
            {
                var info = flexChart.HitTest(new Point(e.Position.X, double.NaN));
                int pointIndex = info.PointIndex;
                xLabel.Text = string.Format("{0:dd-MM}", info.X);

                for (int index = 0; index < flexChart.Series.Count; index++)
                {
                    var series = flexChart.Series[index];
                    var value = series.GetValues(0)[pointIndex];

                    var fill = (int)((IChart)flexChart).GetColor(index);
                    string content = string.Format("{0} = {1}", series.SeriesName, string.Format("{0:f0}", value));
                    Label yLabel = yLabels[index];
                    yLabel.Text = content;
                }
            }
        }
        public class LineMarkerViewModel
        {
            const int Count = 300;
            Random rnd = new Random();

            public List<LineMarkerSampleDataItem> Items
            {
                get
                {
                    List<LineMarkerSampleDataItem> items = new List<LineMarkerSampleDataItem>();
                    DateTime date = new DateTime(2016, 1, 1);
                    for (var i = 0; i < Count; i++)
                    {
                        var item = new LineMarkerSampleDataItem()
                        {
                            Date = date.AddDays(i),
                            Input = rnd.Next(10, 20),
                            Output = rnd.Next(0, 10)
                        };
                        items.Add(item);
                    }
                    return items;
                }
            }
            public List<string> LineType
            {
                get
                {
                    return Enum.GetNames(typeof(LineMarkerLines)).ToList();
                }
            }
            public List<string> LineMarkerInteraction
            {
                get
                {
                    return Enum.GetNames(typeof(LineMarkerInteraction)).ToList();
                }
            }
        }
        public class LineMarkerSampleDataItem
        {
            public int Input { get; set; }
            public int Output { get; set; }
            public DateTime Date { get; set; }
        }
    }