Binding of a Polyline. What am I doing wrong?

I am trying what I thought a simple thing: drawing lines of a list of point. If I put the list statically in the xaml of my window everything is ok. If I do the bind, then nothing is displayed.

the window code:

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*" />
        <ColumnDefinition Width="*" />
    </Grid.ColumnDefinitions>
    <Polyline Stretch="Fill" Grid.Column="0" Name="polyline" Stroke="Red" DataContext="{Binding Points}">
    </Polyline>   
</Grid>

public partial class testWindow2 : Window
{
    AudioS开发者_JAVA百科ignalModelView audioSignalModelView;

    public testWindow2()
    {
        InitializeComponent();

        audioSignalModelView = new AudioSignalModelView();

        this.DataContext = audioSignalModelView;
    }
}

public class AudioSignalModelView
{
    public AudioSignalModelView()
    {
        Point pointA = new Point {X=0,Y=0};
        Point pointB = new Point { X = 0.2, Y = 0.4 };
        Point pointC = new Point { X = 0.8, Y = 0.1 };
        Point pointD = new Point { X = 1, Y = 1 };

        Points.Add(pointA);
        Points.Add(pointB);
        Points.Add(pointC);
        Points.Add(pointD);
    }

    private AudioSignalTest audioSignalTest;

    private PointCollection _points = new PointCollection();
    public PointCollection Points
    {
        get { return _points; }
    }
}

I think the binding is done somehow, because if I put a breakpoint in the getter of the Points property, it is called by the system...

What is obviously wrong in my code ?

You want to bind to the Points property not the DataContext.

<Polyline Stretch="Fill" Grid.Column="0"
          Name="polyline" Stroke="Red"
          Points="{Binding Points}">  <-- Here
</Polyline>   

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