Taking an example that Graham had posted awhile back, I am using a DataTemplate to bind the Width/Height of an Ellipse marker based on the underlying data.  Something like this:

<UserControl.Resources>

        <DataTemplate x:Key="bubbleTemplate" >

            <Ellipse Stretch="Fill" 

                     HorizontalAlignment="Stretch" 

                     VerticalAlignment="Stretch" 

                     Fill="{Binding ActualItemBrush}" 

                     Stroke="{Binding Series.ActualMarkerOutline}" 

                     StrokeThickness="0.5" 

                     MinWidth="10" MinHeight="10" 

                     Width="{Binding Item.Width}"

                     Height="{Binding Item.Width}"/>

        </DataTemplate>

    </UserControl.Resources>

    <Grid x:Name="LayoutRoot" Background="White">

        <igChart:XamDataChart x:Name="theChart">

            <igChart:XamDataChart.Axes>

                <igChart:NumericXAxis x:Name="xAxis" 

                                      MinimumValue="0" MaximumValue="15"/>

                <igChart:NumericYAxis x:Name="yAxis" 

                                      MinimumValue="0" MaximumValue="15"/>

            </igChart:XamDataChart.Axes>

            <igChart:XamDataChart.Series>

                <igChart:ScatterSeries x:Name="scatter"

                                       MarkerTemplate="{StaticResource bubbleTemplate}"

                                       ItemsSource="{Binding}"

                                       XMemberPath="XValue"

                                       YMemberPath="YValue"

                                       XAxis="{Binding ElementName=xAxis}"

                                       YAxis="{Binding ElementName=yAxis}"/>

            </igChart:XamDataChart.Series>

        </igChart:XamDataChart>

    </Grid>

and in the code behind I have a class with the Width property.

I've got some code that does the hit test on a series left mouse button up and set's the Selected property on the item.  Something like this:

if (hitItems.Count ==1)

{

   var item = e.Item

   MyDataPoint dp  = e.Item as MyDataPoint;

   dp.Selected = !dp.Selected;

}

In the MyDataPoint class, I've the Selected and Width properties look like so:

public class MyDataPoint : INotifyPropertyChanged

{

   public event PropertyChangedEventHander PropertyChanged;

        public double Width 

        {

            get { return _width; }

            set

            {

                _width = value;

                OnPropertyChanged("Width");

            }

        }

        private bool _selected = false;

        public bool Selected

        {

            get { return _selected; }

            set

            { 

                _selected = value;

                if (_selected)

                {

                    Width = SELECTEDSIZE;

                }

                else

                {

                    Width = UNSELECTEDSIZE;

                }

            }

        }

Now, the idea is that if I a point to Selected, the corresponding marker will change size.  This does work but the behavior that I'm seeing is as follows:

I set point 1 to selected and it resizes but it's center isn't correct.

I set point 2 to selected and now it resizes but it's center isn't correct either.  But point 1 has now adjusted its center to be correct.

Ideas on how to force the series to adjust the point?  

Thanks,

Matt