Tracker Format for Custom data points

I have a quick question about custom tracker formats. I have created a ScatterSeries in my view model like so:

Series = new ScatterSeries());
Series.TrackerFormatString = "match: {Match}";

and I'd like this match data to come from my data point, so I have a custom datapoint class like this:

public class MyDataPoint : ScatterPoint {
  public string Match {get;set;}
  public MyDataPoint(double x, double y, string match):base(x,y) { Match = match; }
}

and then I add these points to the scatter series like this:

Series.Points.Add(new MyDataPoint(5,10,"Message about this"));

But when I click on these points, I get a Null reference exception from PlotView and the program crashes.

I thought I used the wrong TrackerFormatString so tried this one but it had the same result

Series.TrackerFormatString = "Match {DataPoint.Match}";

How've I gone wrong here?

I have the same problem using ScatterPoint as base with a similar implementation.

In previous projects I used IDataPoint, but that seems to be removed now..

Yes, and it seems weird to me that the HitResult that goes into TrackerEventArgs for the TrackerChanged event has a DataPoint when the Series type is ScatterSeries. Shouldn't this be a ScatterPoint? I guess with the IDataPoint interface gone there isn't a good way to do polymorphism between DataPoint's and ScatterPoint's. I suppose this means that before the when the HitResult is constructed the X and Y from the ScatterPoint are copied to the a newly constructed DataPoint? Not sure, maybe I'll look at the code today.

Look some more on this after my vacation and solved my problem after finding the CustomTrackerDemo..

In my XAML I added:

<oxy:PlotView ... >
                <oxy:PlotView.DefaultTrackerTemplate>
                    <ControlTemplate>
                        <oxy:TrackerControl Position="{Binding Position}" LineExtents="{Binding LineExtents}">
                            <oxy:TrackerControl.Content>
                                <TextBlock Text="{Binding}" Margin="8"/>
                            </oxy:TrackerControl.Content>
                        </oxy:TrackerControl>
                    </ControlTemplate>
                </oxy:PlotView.DefaultTrackerTemplate>
</oxy:PlotView>

In my viewmodel I have a ScatterSeries

 var scatterSeries = new ScatterSeries
      {
        ...
        TrackerFormatString = "{ToolTip}"
      };
      

which I add a custom data point to

 public class ScatterPointWithToolTip : ScatterPoint
  {
    public string ToolTip { get; private set; }

    public ScatterPointWithToolTip(double x, double y, ...., object tooltip) 
      : base(x, y...)
    {
      ToolTip = (string) tooltip;
    }
  }