Are those scatter line series or line series? Which axes are you using? How many data points are in each series?  That behavior is strange, but we might need to have more information about your data to replicate. Can you provide a sample?

Thanks,

Graham

Hi Graham,

                    The above presented solution is in silverlight I think. Actually I am working on WPF can you please provide me a wpf version as well.

Thanks.

Hi,

Have you had any trouble running the above in WPF? It should run in Silverlight or WPF and if there are changes required they would be relatively minor. The above extends a user control so you could either paste the code into a user control, or change any references to user control to window, and you could name the control MainWindow rather than MainPage.

-Graham

Hi,

There were a few things that weren't working appropriately for WPF. Here is an improved version:

    <Window.Resources>
        <local:TestData x:Key="vm" />
    </Window.Resources>
    <Grid x:Name="LayoutRoot" Background="White">
        <igChart:XamDataChart x:Name="chart" VerticalZoomable="True" HorizontalZoomable="True" >
            <local:ChartBehaviors.ChartPoints>
                <local:ChartPointsBehavior>
                    <local:ChartPointsBehavior.PointTemplate>
                        <DataTemplate>
                            <Grid >
                                <Grid x:Name="container" Width="6" Height="6"/>
                                <!--<ContentPresenter Margin="6,6,6,6"     
                                    HorizontalAlignment="Stretch"     
                                    VerticalAlignment="Stretch">
                                </ContentPresenter>-->
                                <!--<Popup IsOpen="True" DataContext="{Binding}"
                                       AllowsTransparency="True"
                                       PlacementTarget="{Binding ElementName=container}"
                                       Placement="Relative">-->
                                <Canvas Width="0" Height="0">
                                    <Path Data="M 1,1 L 17,17" Stroke="Black" StrokeThickness=".5" />
                                    <Border Margin="12,12" Background="White"    
                                                CornerRadius="5"  
                                                BorderThickness=".5"  
                                                BorderBrush="Black"  
                                                    >
                                        <TextBlock Margin="3" Text="{Binding Data.Label}" />
                                    </Border>
                                </Canvas>
                                <!--</Popup>-->
                            </Grid>
                        </DataTemplate>
                    </local:ChartPointsBehavior.PointTemplate>
                    <local:ChartPointsBehavior.Points>
                        <local:PointInfo          
                            X="1"          
                            Y="2"
                            DataIndex="1">
                        </local:PointInfo>

                        <local:PointInfo          
                            X="3"          
                            Y="4"
                            DataIndex="3">
                        </local:PointInfo>
                    </local:ChartPointsBehavior.Points>
                </local:ChartPointsBehavior>
            </local:ChartBehaviors.ChartPoints>

            <igChart:XamDataChart.Axes>
                <igChart:CategoryXAxis x:Name="xAxis" ItemsSource="{StaticResource vm}" Label="{}{Label}" />
                <igChart:NumericYAxis x:Name="yAxis" />
            </igChart:XamDataChart.Axes>
            <igChart:XamDataChart.Series>
                <igChart:LineSeries x:Name="line"        
                               MarkerType="Triangle"     
                               XAxis="{Binding ElementName=xAxis}"        
                               YAxis="{Binding ElementName=yAxis}"        
                               ValueMemberPath="Value"        
                               ItemsSource="{StaticResource vm}"/>
            </igChart:XamDataChart.Series>
        </igChart:XamDataChart>
    </Grid>

public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }
    }

    public class TestData
        : ObservableCollection<TestDataItem>
    {
        public TestData()
        {
            Add(new TestDataItem() { Label = "1", Value = 1 });
            Add(new TestDataItem() { Label = "2", Value = 2 });
            Add(new TestDataItem() { Label = "3", Value = 3 });
            Add(new TestDataItem() { Label = "4", Value = 4 });
            Add(new TestDataItem() { Label = "5", Value = 5 });
            Add(new TestDataItem() { Label = "6", Value = 6 });
            Add(new TestDataItem() { Label = "7", Value = 7 });
        }
    }

    public class TestDataItem
    {
        public string Label { get; set; }
        public double Value { get; set; }
    }

    public class ChartBehaviors
        : DependencyObject
    {
        public static readonly DependencyProperty ChartPointsProperty =
            DependencyProperty.RegisterAttached("ChartPoints",
            typeof(ChartPointsBehavior), typeof(ChartBehaviors),
            new PropertyMetadata(null,
                (o, e) => CursorTooltipChanged(
                    o as XamDataChart,
                    e.OldValue as ChartPointsBehavior,
                    e.NewValue as ChartPointsBehavior)));

        public static ChartPointsBehavior GetChartPoints(
            DependencyObject target)
        {
            return target.GetValue(ChartPointsProperty)
                as ChartPointsBehavior;
        }

        public static void SetChartPoints(
            DependencyObject target, ChartPointsBehavior behavior)
        {
            target.SetValue(ChartPointsProperty, behavior);
        }

        private static void CursorTooltipChanged(
            XamDataChart chart,
            ChartPointsBehavior oldValue,
            ChartPointsBehavior newValue)
        {
            if (chart == null)
            {
                return;
            }
            if (oldValue != null)
            {
                oldValue.OnDetach(chart);
            }
            if (newValue != null)
            {
                newValue.OnAttach(chart);
            }
        }

    }

    public class PointInfo
        : FrameworkElement
    {
        public PointInfo()
        {
            _id = Guid.NewGuid();
            X = double.NaN;
            Y = double.NaN;
        }

        private PointInfo(Guid id)
        {
            _id = id;
            X = double.NaN;
            Y = double.NaN;
        }

        private Guid _id;
        public Guid Id
        {
            get { return _id; }
            private set { _id = value; }
        }

        public double X { get; set; }
        public double Y { get; set; }
        public string Label { get; set; }

        public Brush Fill { get; set; }

        public DataTemplate PointTemplate { get; set; }

        public static readonly DependencyProperty DataProperty =
            DependencyProperty.Register(
            "Data",
            typeof(object),
            typeof(PointInfo),
            new PropertyMetadata(null));

        public object Data
        {
            get { return GetValue(DataProperty); }
            set { SetValue(DataProperty, value); }
        }

        public static readonly DependencyProperty DataIndexProperty =
        DependencyProperty.Register(
        "DataIndex",
        typeof(int),
        typeof(PointInfo),
        new PropertyMetadata(-1));

        public int DataIndex
        {
            get { return (int)GetValue(DataIndexProperty); }
            set { SetValue(DataIndexProperty, value); }
        }

        public PointInfo Clone()
        {
            PointInfo newPointInfo = new PointInfo(_id);
            newPointInfo.X = X;
            newPointInfo.Y = Y;
            newPointInfo.Label = Label;
            newPointInfo.PointTemplate = PointTemplate;
            newPointInfo.Fill = Fill;
            newPointInfo.DataIndex = DataIndex;

            BindingOperations.SetBinding(
                newPointInfo,
                PointInfo.DataProperty,
                new Binding("Data")
                {
                    Source = this
                });
            return newPointInfo;
        }
    }

    public class PointInfoCollection
        : ObservableCollection<PointInfo>
    {

    }

    public class ChartPointsBehavior
        : DependencyObject
    {
        public ChartPointsBehavior()
        {
            Points = new PointInfoCollection();
        }

        public static readonly DependencyProperty StripsProperty =
            DependencyProperty.Register("Points",
            typeof(PointInfoCollection),
            typeof(ChartPointsBehavior),
            new PropertyMetadata(null,
                (o, e) =>
                    (o as ChartPointsBehavior)
                    .OnPointsChanged(
                    e.OldValue as PointInfoCollection,
                    e.NewValue as PointInfoCollection)));

        public PointInfoCollection Points
        {
            get { return (PointInfoCollection)GetValue(StripsProperty); }
            set { SetValue(StripsProperty, value); }
        }

        public DataTemplate PointTemplate { get; set; }

        private void OnPointsChanged(
            PointInfoCollection oldValue,
            PointInfoCollection newValue)
        {
            if (oldValue != null)
            {
                oldValue.CollectionChanged -= Points_CollectionChanged;
            }

            if (newValue != null)
            {
                newValue.CollectionChanged += Points_CollectionChanged;
            }
            RefreshPoints();
        }

        void Points_CollectionChanged(
            object sender,
            NotifyCollectionChangedEventArgs e)
        {
            RefreshPoints();
        }

        private XamDataChart _owner = null;

        public void OnAttach(XamDataChart chart)
        {
            if (_owner != null)
            {
                OnDetach(_owner);
            }
            _owner = chart;

            _owner.WindowRectChanged += Owner_WindowRectChanged;
            _owner.SizeChanged += Owner_SizeChanged;
            _owner.Axes.CollectionChanged += Axes_CollectionChanged;
            _owner.Axes.CollectionResetting += Axes_CollectionResetting;

            RefreshPoints();
        }

        void Owner_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            RefreshPoints();
        }

        void Axes_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            if (e.OldItems != null)
            {
                foreach (Axis axis in e.OldItems)
                {
                    axis.SizeChanged -= Axis_SizeChanged;
                }
            }
            if (e.NewItems != null)
            {
                foreach (Axis axis in e.NewItems)
                {
                    axis.SizeChanged += Axis_SizeChanged;
                }
            }
            RefreshPoints();
        }

        void Axis_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            RefreshPoints();
        }

        void Axes_CollectionResetting(object sender, EventArgs e)
        {
            foreach (Axis axis in _owner.Axes)
            {
                axis.SizeChanged -= Axis_SizeChanged;
            }
            RefreshPoints();
        }

        void Owner_WindowRectChanged(object sender, Infragistics.RectChangedEventArgs e)
        {
            RefreshPoints();
        }

        private void GetAxes(
            out Axis xAxis,
            out Axis yAxis)
        {
            if (_owner == null)
            {
                xAxis = null;
                yAxis = null;
                return;
            }

            xAxis =
               (from axis in _owner.Axes
                where axis is NumericXAxis ||
                axis is CategoryXAxis ||
                axis is CategoryDateTimeXAxis
                select axis).FirstOrDefault();

            yAxis =
                (from axis in _owner.Axes
                 where axis is NumericYAxis
                 select axis).FirstOrDefault();
        }

        private Series GetSeries()
        {
            if (_owner == null)
            {
                return null;
            }

            return _owner.Series.FirstOrDefault();
        }

        private void ClearExisting()
        {
            var series = GetSeries();
            if (series == null)
            {
                return;
            }
            if (series.RootCanvas == null)
            {
                return;
            }
            var existing =
               from child in series.RootCanvas.Children
                   .OfType<ContentControl>()
               where child.Content != null &&
               child.Content is PointInfo
               select child;
            existing.ToList().ForEach(
                (ele) => series.RootCanvas.Children.Remove(ele));
        }

        private void RefreshPoints()
        {
            Axis xAxis;
            Axis yAxis;
            GetAxes(out xAxis, out yAxis);

            if (xAxis == null || yAxis == null || xAxis.RootCanvas == null)
            {
                return;
            }

            ClearExisting();

            Rect viewport = GetViewportRect(xAxis);

            foreach (PointInfo info in Points)
            {
                PointInfo toAdd = info.Clone();
                if (double.IsNaN(toAdd.X))
                {
                    toAdd.X = viewport.Left;
                }
                else
                {
                    toAdd.X =
                        xAxis.GetScaledValue(
                        toAdd.X, _owner.WindowRect, viewport);
                }

                if (double.IsNaN(toAdd.Y))
                {
                    toAdd.Y = viewport.Top;
                }
                else
                {
                    toAdd.Y =
                        yAxis.GetScaledValue(
                        toAdd.Y, _owner.WindowRect, viewport);
                }

                if (toAdd.PointTemplate == null)
                {
                    toAdd.PointTemplate = this.PointTemplate;
                }

                if (toAdd.PointTemplate != null &&
                    !double.IsNaN(toAdd.Y) &&
                    !double.IsInfinity(toAdd.Y) &&
                    !double.IsNaN(toAdd.X) &&
                    !double.IsInfinity(toAdd.X))
                {
                    var series = GetSeries();
                    if (series == null)
                    {
                        continue;
                    }
                    var pointControl = new ContentControl();
                    Canvas.SetZIndex(pointControl, 2000);
                    if (toAdd.DataIndex >= 0)
                    {
                        toAdd.SetBinding(
                            PointInfo.DataProperty,
                            new Binding(
                                "ItemsSource[" +
                                toAdd.DataIndex +
                                "]")
                                {
                                    Source = series
                                });
                    }
                    pointControl.ContentTemplate = toAdd.PointTemplate;
                    pointControl.Content = toAdd;


                    series.RootCanvas.Children.Add(pointControl);

                    pointControl.Measure(
                        new Size(
                            double.PositiveInfinity,
                            double.PositiveInfinity));

                    Canvas.SetLeft(pointControl,
                        toAdd.X -
                        (pointControl.DesiredSize.Width / 2.0));
                    Canvas.SetTop(pointControl,
                        toAdd.Y -
                        (pointControl.DesiredSize.Height / 2.0));
                }
            }
        }

        private Rect GetViewportRect(
            Axis axis)
        {
            double top = 0;
            double bottom = axis.ActualHeight;
            double left = 0;
            double right = axis.ActualWidth;

            double width = right - left;
            double height = bottom - top;

            if (width > 0.0 && height > 0.0)
            {
                return new Rect(left, top, width, height);
            }
            return Rect.Empty;
        }

        public void OnDetach(XamDataChart chart)
        {
            if (_owner != chart)
            {
                return;
            }

            _owner.WindowRectChanged -= Owner_WindowRectChanged;
            _owner.SizeChanged -= Owner_SizeChanged;
            _owner.Axes.CollectionChanged -= Axes_CollectionChanged;
            _owner.Axes.CollectionResetting -= Axes_CollectionResetting;

            Axis xAxis;
            Axis yAxis;
            GetAxes(out xAxis, out yAxis);

            if (xAxis == null || yAxis == null)
            {
                return;
            }

            ClearExisting();

            _owner = null;
        }
    }

Hope this helps!

-Graham

Ditto for me.  Working great now.  Thanks Graham!

Gary

HI Graham,

                   Thanks for the solution. Thats exactly what I was looking for.

Here's a version that uses a separate canvas for the annotations:
Code behind:

public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void click_Click(object sender, RoutedEventArgs e)
        {
            (Resources["vm"] as TestData)[1].Value++;
        }
    }

    public class TestData
         : ObservableCollection<TestDataItem>
    {
        public TestData()
        {
            Add(new TestDataItem() { Label = "1", Value = 1 });
            Add(new TestDataItem() { Label = "2", Value = 2 });
            Add(new TestDataItem() { Label = "3", Value = 3 });
            Add(new TestDataItem() { Label = "4", Value = 4 });
            Add(new TestDataItem() { Label = "5", Value = 5 });
            Add(new TestDataItem() { Label = "6", Value = 6 });
            Add(new TestDataItem() { Label = "7", Value = 7 });
        }
    }

    public class TestDataItem
        : INotifyPropertyChanged
    {
        private string _label;
        public string Label
        {
            get { return _label; }
            set { _label = value; RaisePropertyChanged("Label"); }
        }

        private double _value;
        public double Value
        {
            get { return _value; }
            set { _value = value; RaisePropertyChanged("Value"); }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        private void RaisePropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(
                    this, 
                    new PropertyChangedEventArgs(propertyName));
            }
        }
    }

    public class ChartBehaviors
        : DependencyObject
    {
        public static readonly DependencyProperty ChartPointsProperty =
            DependencyProperty.RegisterAttached("ChartPoints",
            typeof(ChartPointsBehavior), typeof(ChartBehaviors),
            new PropertyMetadata(null,
                (o, e) => CursorTooltipChanged(
                    o as XamDataChart,
                    e.OldValue as ChartPointsBehavior,
                    e.NewValue as ChartPointsBehavior)));

        public static ChartPointsBehavior GetChartPoints(
            DependencyObject target)
        {
            return target.GetValue(ChartPointsProperty)
                as ChartPointsBehavior;
        }

        public static void SetChartPoints(
            DependencyObject target, ChartPointsBehavior behavior)
        {
            target.SetValue(ChartPointsProperty, behavior);
        }

        private static void CursorTooltipChanged(
            XamDataChart chart,
            ChartPointsBehavior oldValue,
            ChartPointsBehavior newValue)
        {
            if (chart == null)
            {
                return;
            }
            if (oldValue != null)
            {
                oldValue.OnDetach(chart);
            }
            if (newValue != null)
            {
                newValue.OnAttach(chart);
            }
        }

    }

    public class PointInfo
        : FrameworkElement
    {
        public PointInfo()
        {
            _id = Guid.NewGuid();
            X = double.NaN;
            Y = double.NaN;
        }

        private PointInfo(Guid id)
        {
            _id = id;
            X = double.NaN;
            Y = double.NaN;
        }

        private Guid _id;
        public Guid Id
        {
            get { return _id; }
            private set { _id = value; }
        }

        public static readonly DependencyProperty XProperty =
           DependencyProperty.Register(
           "X",
           typeof(double),
           typeof(PointInfo),
           new PropertyMetadata(0.0,
               (o, e) => (o as PointInfo).OnPropertyChanged(
                   "X", e.OldValue, e.NewValue)));

        private void OnPropertyChanged(string propertyName, object oldValue, object newValue)
        {
            if (Owner != null)
            {
                Owner.SignalNeedsRefresh();
            }
        }

        public double X
        {
            get { return (double)GetValue(XProperty); }
            set { SetValue(XProperty, value); }
        }

        public static readonly DependencyProperty YProperty =
           DependencyProperty.Register(
           "Y",
           typeof(double),
           typeof(PointInfo),
           new PropertyMetadata(0.0,
               (o, e) => (o as PointInfo).OnPropertyChanged(
                   "Y", e.OldValue, e.NewValue)));

        public double Y
        {
            get { return (double)GetValue(YProperty); }
            set { SetValue(YProperty, value); }
        }

        public static readonly DependencyProperty LabelProperty =
           DependencyProperty.Register(
           "Label",
           typeof(string),
           typeof(PointInfo),
           new PropertyMetadata("",
               (o, e) => (o as PointInfo).OnPropertyChanged(
                   "Label", e.OldValue, e.NewValue)));

        public string Label
        {
            get { return (string)GetValue(LabelProperty); }
            set { SetValue(LabelProperty, value); }
        }

        public Brush Fill { get; set; }

        public DataTemplate PointTemplate { get; set; }

        public static readonly DependencyProperty DataProperty =
            DependencyProperty.Register(
            "Data",
            typeof(object),
            typeof(PointInfo),
            new PropertyMetadata(null,
               (o, e) => (o as PointInfo).OnPropertyChanged(
                   "Data", e.OldValue, e.NewValue)));

        public object Data
        {
            get { return GetValue(DataProperty); }
            set { SetValue(DataProperty, value); }
        }

        public static readonly DependencyProperty DataIndexProperty =
        DependencyProperty.Register(
        "DataIndex",
        typeof(int),
        typeof(PointInfo),
        new PropertyMetadata(-1,
               (o, e) => (o as PointInfo).OnPropertyChanged(
                   "DataIndex", e.OldValue, e.NewValue)));

        public int DataIndex
        {
            get { return (int)GetValue(DataIndexProperty); }
            set { SetValue(DataIndexProperty, value); }
        }

        public static readonly DependencyProperty SeriesIndexProperty =
        DependencyProperty.Register(
        "SeriesIndex",
        typeof(int),
        typeof(PointInfo),
        new PropertyMetadata(0,
              (o, e) => (o as PointInfo).OnPropertyChanged(
                  "SeriesIndex", e.OldValue, e.NewValue)));

        public int SeriesIndex
        {
            get { return (int)GetValue(SeriesIndexProperty); }
            set { SetValue(SeriesIndexProperty, value); }
        }

        public PointInfo Clone()
        {
            PointInfo newPointInfo = new PointInfo(_id);
            newPointInfo.X = X;
            newPointInfo.Y = Y;
            newPointInfo.Label = Label;
            newPointInfo.PointTemplate = PointTemplate;
            newPointInfo.Fill = Fill;
            newPointInfo.DataIndex = DataIndex;

            BindingOperations.SetBinding(
                newPointInfo,
                PointInfo.DataProperty,
                new Binding("Data")
                {
                    Source = this
                });
            return newPointInfo;
        }

        public PointInfoCollection Owner { get; set; }
    }

    public class PointInfoCollection
        : ObservableCollection<PointInfo>
    {
        protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
        {
            base.OnCollectionChanged(e);

            if (e.OldItems != null)
            {
                foreach (var item in e.OldItems.OfType<PointInfo>())
                {
                    item.Owner = null;
                }
            }

            if (e.NewItems != null)
            {
                foreach (var item in e.NewItems.OfType<PointInfo>())
                {
                    item.Owner = this;
                }
            }
        }

        internal void SignalNeedsRefresh()
        {
            if (NeedsRefresh != null)
            {
                NeedsRefresh(this);
            }
        }

        public delegate void NeedsRefreshEventHandler(object o);

        public event NeedsRefreshEventHandler NeedsRefresh;
    }

    public class AnnotationCanvas
        : Canvas
    {

    }

    public class ChartPointsBehavior
        : DependencyObject
    {
        public ChartPointsBehavior()
        {
            Points = new PointInfoCollection();
        }

        public static readonly DependencyProperty StripsProperty =
            DependencyProperty.Register("Points",
            typeof(PointInfoCollection),
            typeof(ChartPointsBehavior),
            new PropertyMetadata(null,
                (o, e) =>
                    (o as ChartPointsBehavior)
                    .OnPointsChanged(
                    e.OldValue as PointInfoCollection,
                    e.NewValue as PointInfoCollection)));

        public PointInfoCollection Points
        {
            get { return (PointInfoCollection)GetValue(StripsProperty); }
            set { SetValue(StripsProperty, value); }
        }

        public DataTemplate PointTemplate { get; set; }

        private void OnPointsChanged(
            PointInfoCollection oldValue,
            PointInfoCollection newValue)
        {
            if (oldValue != null)
            {
                oldValue.CollectionChanged -= Points_CollectionChanged;
                oldValue.NeedsRefresh -= NewValue_NeedsRefresh;
            }

            if (newValue != null)
            {
                newValue.CollectionChanged += Points_CollectionChanged;
                newValue.NeedsRefresh += NewValue_NeedsRefresh;
            }
            RefreshPoints();
        }

        void NewValue_NeedsRefresh(object o)
        {
            RefreshPoints();
        }

        void Points_CollectionChanged(
            object sender,
            NotifyCollectionChangedEventArgs e)
        {
            RefreshPoints();
        }

        private XamDataChart _owner = null;
        private AnnotationCanvas _canvas = null;

        public void OnAttach(XamDataChart chart)
        {
            if (_owner != null)
            {
                OnDetach(_owner);
            }
            _owner = chart;

            _owner.WindowRectChanged += Owner_WindowRectChanged;
            _owner.SizeChanged += Owner_SizeChanged;
            _owner.Axes.CollectionChanged += Axes_CollectionChanged;
            _owner.Axes.CollectionResetting += Axes_CollectionResetting;

            RefreshPoints();
        }

        void Owner_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            RefreshPoints();
        }

        void Axes_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            if (e.OldItems != null)
            {
                foreach (Axis axis in e.OldItems)
                {
                    axis.SizeChanged -= Axis_SizeChanged;
                }
            }
            if (e.NewItems != null)
            {
                foreach (Axis axis in e.NewItems)
                {
                    axis.SizeChanged += Axis_SizeChanged;
                }
            }
            RefreshPoints();
        }

        void Axis_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            RefreshPoints();
        }

        void Axes_CollectionResetting(object sender, EventArgs e)
        {
            foreach (Axis axis in _owner.Axes)
            {
                axis.SizeChanged -= Axis_SizeChanged;
            }
            RefreshPoints();
        }

        void Owner_WindowRectChanged(object sender, Infragistics.RectChangedEventArgs e)
        {
            RefreshPoints();
        }

        private void GetAxes(
            out Axis xAxis,
            out Axis yAxis)
        {
            if (_owner == null)
            {
                xAxis = null;
                yAxis = null;
                return;
            }

            xAxis =
               (from axis in _owner.Axes
                where axis is NumericXAxis ||
                axis is CategoryXAxis ||
                axis is CategoryDateTimeXAxis
                select axis).FirstOrDefault();

            yAxis =
                (from axis in _owner.Axes
                 where axis is NumericYAxis
                 select axis).FirstOrDefault();
        }

        private Series GetSeries()
        {
            if (_owner == null)
            {
                return null;
            }

            return _owner.Series.FirstOrDefault();
        }

        private AnnotationCanvas GetCanvas()
        {
            if (_canvas != null)
            {
                return _canvas;
            }

            Series series = GetSeries();
            if (series == null)
            {
                return null;
            }

            Panel parent = series.Parent as Panel;
            if (parent == null)
            {
                return null;
            }

            _canvas = new AnnotationCanvas();
            Canvas.SetZIndex(_canvas, 10000);
            parent.Children.Add(_canvas);

            return _canvas;
        }

        private void RemoveCanvas()
        {
            if (_canvas == null)
            {
                return;
            }

            Panel parent = _canvas.Parent as Panel;
            if (parent == null)
            {
                _canvas = null;
                return;
            }

            parent.Children.Remove(_canvas);
            _canvas = null;
        }

        private void ClearExisting()
        {
            var canvas = GetCanvas();
            if (canvas == null)
            {
                return;
            }

            var existing =
               from child in canvas.Children
                   .OfType<ContentControl>()
               where child.Content != null &&
               child.Content is PointInfo
               select child;
            existing.ToList().ForEach(
                (ele) => canvas.Children.Remove(ele));
        }

        private void RefreshPoints()
        {
            Axis xAxis;
            Axis yAxis;
            GetAxes(out xAxis, out yAxis);

            if (xAxis == null || yAxis == null || xAxis.RootCanvas == null)
            {
                return;
            }

            ClearExisting();

            Rect viewport = GetViewportRect(xAxis);

            foreach (PointInfo info in Points)
            {
                PointInfo toAdd = info.Clone();
                if (double.IsNaN(toAdd.X))
                {
                    toAdd.X = viewport.Left;
                }
                else
                {
                    toAdd.X =
                        xAxis.GetScaledValue(
                        toAdd.X, _owner.WindowRect, viewport);
                }

                if (double.IsNaN(toAdd.Y))
                {
                    toAdd.Y = viewport.Top;
                }
                else
                {
                    toAdd.Y =
                        yAxis.GetScaledValue(
                        toAdd.Y, _owner.WindowRect, viewport);
                }

                if (toAdd.PointTemplate == null)
                {
                    toAdd.PointTemplate = this.PointTemplate;
                }

                if (toAdd.PointTemplate != null &&
                    !double.IsNaN(toAdd.Y) &&
                    !double.IsInfinity(toAdd.Y) &&
                    !double.IsNaN(toAdd.X) &&
                    !double.IsInfinity(toAdd.X))
                {
                    var canvas = GetCanvas();
                    if (canvas == null)
                    {
                        continue;
                    }
                    var pointControl = new ContentControl();
                    Canvas.SetZIndex(pointControl, 2000);
                    if (toAdd.DataIndex >= 0 && 
                        toAdd.SeriesIndex >= 0 &&
                        toAdd.SeriesIndex < _owner.Series.Count)
                    {
                        var series = _owner.Series[toAdd.SeriesIndex];
                        toAdd.SetBinding(
                            PointInfo.DataProperty,
                            new Binding(
                                "ItemsSource[" +
                                toAdd.DataIndex +
                                "]")
                            {
                                Source = series
                            });
                    }
                    pointControl.ContentTemplate = toAdd.PointTemplate;
                    pointControl.Content = toAdd;

                    canvas.Children.Add(pointControl);

                    pointControl.Measure(
                        new Size(
                            double.PositiveInfinity,
                            double.PositiveInfinity));

                    Canvas.SetLeft(pointControl,
                        toAdd.X -
                        (pointControl.DesiredSize.Width / 2.0));
                    Canvas.SetTop(pointControl,
                        toAdd.Y -
                        (pointControl.DesiredSize.Height / 2.0));
                }
            }
        }

        private Rect GetViewportRect(
            Axis axis)
        {
            double top = 0;
            double bottom = axis.ActualHeight;
            double left = 0;
            double right = axis.ActualWidth;

            double width = right - left;
            double height = bottom - top;

            if (width > 0.0 && height > 0.0)
            {
                return new Rect(left, top, width, height);
            }
            return Rect.Empty;
        }

        public void OnDetach(XamDataChart chart)
        {
            if (_owner != chart)
            {
                return;
            }

            _owner.WindowRectChanged -= Owner_WindowRectChanged;
            _owner.SizeChanged -= Owner_SizeChanged;
            _owner.Axes.CollectionChanged -= Axes_CollectionChanged;
            _owner.Axes.CollectionResetting -= Axes_CollectionResetting;

            Axis xAxis;
            Axis yAxis;
            GetAxes(out xAxis, out yAxis);

            if (xAxis == null || yAxis == null)
            {
                return;
            }

            ClearExisting();
            RemoveCanvas();

            _owner = null;
        }
    }  

Hope this helps!

-Graham

The current version of that code is storing the annotations in the first series' canvas. Which is z ordered lowest. You can change it to store them in the last series' canvas. By doing something like this:

 private Series GetSeries()
        {
            if (_owner == null)
            {
                return null;
            }

            return _owner.Series.LastOrDefault();
        }

You may also need to change ClearExisting to make sure it checks all series' canvases for annotations to remove if you do things that will reorder the series.

An alternate solution might be to set the ZIndex on the first series to a high number since thats were the annotations are put.

Yet another solution would be to put a new canvas in the parent that holds the series visually, give it a high ZIndex and put the annotations in that.

Does this help?

-Graham