Edit Path Programmatically

Question

Is it possible to edit a path programmatically?

I'm trying to create a userControl which acts as a horizontal meter whose width is dynamic. I have created a path in the xaml and planned on having an int property which controls the width of the meter dynamically. It has rounded edges so I had planned to edit the x coordinates on the right end of the meter to shrink the meter but keep the same rounded corners. I see the Data property on the path but don't understand how I can edit it.

Is there a better approach, perhaps?

score 4 · Accepted Answer · answered Feb 09 '11 at 07:28

If you're setting Path.Data directly, you won't be able to edit it in code behind. If you want to be able to do that, you should use PathGeometry instead. From MSDN

As you can see from the preceding examples, the two mini-languages are very similar. It's always possible to use a PathGeometry in any situation where you could use a StreamGeometry; so which one should you use? Use a StreamGeometry when you don't need to modify the path after creating it; use a PathGeometry if you do need to modify the path.

The following two Path's are equivalent, the later one can be modified in code behind

<!-- Path 1: Using StreamGeometry -->
<Path x:Name="MyPath"
      Stroke="Black"
      StrokeThickness="10"
      Margin="20"
      Data="M 10,10 L 100,10 L 100,200 L 10,200 Z"/>
<!-- Path 2: Using PathGeometry-->
<Path x:Name="MyPath2"
    Stroke="Black"
    StrokeThickness="10"
    Margin="20">
    <Path.Data>
        <PathGeometry>
            <PathGeometry.Figures>
                <PathFigure x:Name="figure1" StartPoint="10, 10" IsClosed="True">
                    <LineSegment x:Name="line1" Point="100, 10"/>
                    <LineSegment x:Name="line2" Point="100, 200"/>
                    <LineSegment x:Name="line3" Point="10, 200"/>
                </PathFigure>
            </PathGeometry.Figures>
        </PathGeometry>
    </Path.Data>
</Path>

To modify MyPath2 in code behind, you can access the PathFigure and LineSegments either by Name

private void MovePathHorizontally()
{
    figure1.StartPoint = new Point(figure1.StartPoint.X + 10, figure1.StartPoint.Y);
    line1.Point = new Point(line1.Point.X + 10, line1.Point.Y);
    line2.Point = new Point(line2.Point.X + 10, line2.Point.Y);
    line3.Point = new Point(line3.Point.X + 10, line3.Point.Y);
}

or like this

private void MovePathHorizontally()
{
    PathGeometry pathGeometry = MyPath2.Data as PathGeometry;
    PathFigureCollection pathFigures = pathGeometry.Figures;
    foreach (PathFigure pathFigure in pathFigures)
    {
        pathFigure.StartPoint = new Point(pathFigure.StartPoint.X + 10, pathFigure.StartPoint.Y);

        PathSegmentCollection pathSegments = pathFigure.Segments;
        foreach (PathSegment pathSegment in pathSegments)
        {
            if (pathSegment is LineSegment)
            {
                LineSegment lineSegment = pathSegment as LineSegment;
                lineSegment.Point = new Point(lineSegment.Point.X + 10, lineSegment.Point.Y);
            }
        }
    }
}

Edit Path Programmatically

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