WPF Graph DataSource

I don't know how many plots I need to graph at runtime, so I make a WPF Graph DataSource binding to the a collection of a collection of points.  The graph binding works fine when I have more than 2 collections of points (2 plots), but I cannot get the graph to bind when there is only one collection of points.  Should this work, or is this approach way off base?

Binding Object:

        private ObservableCollection<ObservableCollection<System.Windows.Point>> _PlotXYData = new ObservableCollection<ObservableCollection<System.Windows.Point>>();
        public ObservableCollection<ObservableCollection<System.Windows.Point>> PlotXYData
        {
            get
            {
                return _PlotXYData;
            }
            set
            {
                _PlotXYData = value;
                RaisePropertyChanged("PlotXYData");
            }
        }

XAML Binding:

<ni:Graph Name="graph1"  DataSource="{Binding Path=ViewModel.PlotXYData}"><ni:Graph.Axes><ni:AxisDouble x:Name="HorizontalAxis1"
                                       Orientation="Horizontal"
                                       Range="{Binding Path=ViewModel.NIGraph.Axes[0].Range}"
                                       Adjuster="FitLoosely"></ni:AxisDouble><ni:AxisDouble x:Name="VerticalAxis1"
                                       Orientation="Vertical"
                                       Range="{Binding Path=ViewModel.NIGraph.Axes[1].Range}"
                                       Adjuster="FitLoosely"></ni:AxisDouble><ni:AxisDouble x:Name="VerticalAxis2"
                                       Orientation="Vertical"
                                       Range="{Binding Path=ViewModel.NIGraph.Axes[2].Range}"
                                       Adjuster="FitLoosely"
                                       Location="Far"
                                       MajorGridLines="{x:Null}"></ni:AxisDouble></ni:Graph.Axes><ni:Graph.Plots><ni:Plot Label="Plots[0]"
                                 VerticalScale="{Binding ElementName=VerticalAxis1}" ><ni:LinePlotRenderer  Stroke="#FF0070B0" /></ni:Plot><ni:Plot Label="Plots[1]"
                                 VerticalScale="{Binding ElementName=VerticalAxis2}" ><ni:LinePlotRenderer Stroke="#FFB90E30" /></ni:Plot></ni:Graph.Plots></ni:Graph>