This is the way how to create a custom drawing:

1.       Create a canvas and add the XamChart to it as a child.

2.       Use mouse event and add a TextBlock to the canvas as a child.

3.       Use GetPosition methods to get pixel position from axis values.

Thanks,

GoranS

See sample below

XAML:

<Grid x:Name="LayoutRoot">
   <Canvas Name="Canvas1" Margin="0,0,0,0">
      <igCA:XamChart Name="Chart1" Width="523" Height="329"/>
   </Canvas>
</Grid>

C#:

protected override void OnMouseDown(System.Windows.Input.MouseButtonEventArgs e)
        {
            double x1 = Chart1.GetPosition(Infragistics.Windows.Chart.AxisType.PrimaryX, 1);
            double y1 = Chart1.GetPosition(Infragistics.Windows.Chart.AxisType.PrimaryY, 10);
            Canvas canvas = Chart1.Scene.GridArea.Content as Canvas;

            TextBlock text = new TextBlock();
            text.Foreground = Brushes.Red;
            text.Text = "Test";
            Canvas.SetLeft(text, x1);
            Canvas.SetTop(text, y1);

            Canvas1.Children.Add(text);

            base.OnMouseDown(e);
        }