Binding LineSeries values to object fields
===

I'm using the 2010 release of the WPF Toolkit for DataVisualization.

If I want to create a LineSeries chart programmatically, this is what I did before. This code works and plots the data successfully:

    public class TrendData {
        public string Group;
        public IEnumerable<KeyValuePair<DateTime, decimal>> Series;
    }
    ...
    //somewhere within my chart update method
    foreach (TrendData line in DataCollection) {
       LineSeries l = new LineSeries() {
          DependentValuePath = "Value",
          IndependentValuePath = "Key",
          Title = line.Group,
          ItemsSource = line.Series
       };
       Chart.Series.Add(l);
    }


This works without issue. However, I want to stored other values with the data points, because I want to display additional information on mouseover of a DataPoint. So I naively tried this:

    public class TrendData {
       public string Group;
       public IEnumerable<PointData> Series;
    }
    public class PointData {
       public DateTime time;
       public decimal rate;
       public int x;
    }
    ...
    //somewhere within my chart update method
    foreach (TrendData line in DataCollection) {
       LineSeries l = new LineSeries() {
          DependentValuePath = "rate",
          IndependentValuePath = "time",
          Title = line.Group,
          ItemsSource = line.Series
       };
       Chart.Series.Add(l);
    }

This doesn't work, instead giving me an InvalidOperationException: "No suitable axis is available for plotting the dependent value." from DataPointSeries.

Ideas? Am I doing this completely wrong?