Draw curved path between two objects on a <Canvas/> in Silverlight - silverlight

Question

I am playing around with some stuff in Silverlight, and I am trying to dynamically draw a curved line between two other objects on a <Canvas/>. I tried doing something like this:
public partial class MainNodeConnection : UserControl
{
private MainNode _sourceNode;
public MainNode SourceNode
{
get { return _sourceNode; }
set { _sourceNode = value; }
}
private ChildNode _targetNode;
public ChildNode TargetNode
{
get { return _targetNode; }
set { _targetNode = value; }
}
private double _sourceX;
private double _sourceY;
private double _targetX;
private double _targetY;
private Path _connection;
public MainNodeConnection()
{
InitializeComponent();
_connection = new Path();
this.Content = _connection;
}
public void UpdateLocations()
{
_sourceX = Canvas.GetLeft(_sourceNode) + (SourceNode.Width/2);
_sourceY = Canvas.GetTop(_sourceNode) + (SourceNode.Height/2);
_targetX = Canvas.GetLeft(_targetNode);
_targetY = Canvas.GetTop(_targetNode);
string pathData = String.Format("M {0},{1} C {2},{3} {4},{5}", _sourceX, _sourceY, _targetX - _sourceX, _targetY - _sourceX, _targetX, _targetY);
PathGeometry geoData = new PathGeometry();
PathFigure pFigure = new PathFigure();
pFigure.StartPoint = new Point(_sourceX, _sourceY);
BezierSegment pseg = new BezierSegment();
pseg.Point1 = new Point(_targetX - _sourceX, _targetY - _sourceY);
pFigure.Segments.Add(pseg);
geoData.Figures.Add(pFigure);
_connection.Stroke = new SolidColorBrush(Colors.Black);
_connection.StrokeThickness = 1;
_connection.Data = geoData;
this.Content = _connection;
}
}
and I built the objects on the <Canvas/> like this:
public partial class MainPage : UserControl
{
public MainPage()
{
InitializeComponent();
Loaded += new RoutedEventHandler(MainPage_Loaded);
}
void MainPage_Loaded(object sender, RoutedEventArgs e)
{
MainNodeConnection mnc = new MainNodeConnection();
mnc.Width = 300;
mnc.Height = 300;
Canvas.SetLeft(mnc, Canvas.GetLeft(mainNode1));
Canvas.SetTop(mnc, Canvas.GetTop(mainNode1));
mnc.SourceNode = mainNode1;
mnc.TargetNode = childNode1;
nodeCanvas.Children.Add(mnc);
mnc.UpdateLocations();
}
}
the problem I have is I can't get the line to show up. Can anyone spot what I'm doing wrong, or is there a different/better way to do this?

Answer 1

You're missing Point2 and Point3 in the Bezier curve.
From the help file:
A cubic Bezier curve is defined by
four points: a start point, an end
point (Point3), and two control points
(Point1 and Point2). The BezierSegment
class does not contain a property for
the starting point of the curve; it
only defines the end point. The
beginning point of the curve is the
current point of the PathFigure to
which the BezierSegment is added.
The two control points of a cubic
Bezier curve behave like magnets,
attracting portions of what would
otherwise be a straight line toward
themselves and producing a curve. The
first control point, Point1, affects
the beginning portion of the curve;
the second control point, Point2,
affects the ending portion of the
curve. Note that the curve doesn't
necessarily pass through either of the
control points; each control point
moves its portion of the line toward
itself, but not through itself.