(Note: The project is in Silverlight, but if you copy and paste the code into a WPF project, it should work without any changes)

Have you ever wanted to create a Path programmatically or create a Path in code behind or dynamically build a Path or hand code a Path in Silverlight or WPF?

Yes, I just said the same thing 4 different ways, but I’m trying to cast a wide net for Google to catch. One of the biggest troubles I have when I’m trying to do something new is that I don’t always know the proper terminology, so I try to think of all the ways people might want to ask the question.

I’ve been playing around with a good number of information visualization concepts recently and one thing that I’ve found that I needed was the ability to create a path programmatically.

One way to do that is to tackle and fully grok the Path data code system. (Good guides to it are here and here.) This system is really cool, but (unless I’ve missed something) they cannot be animated.

I wanted to build a path based off a data set, but that means that I have to build it programmatically. I didn’t find a lot of useful stuff on how to do this, so I thought I’d throw some out there.

First, because I’m a XAML guy, I’m going to provide a simple XAML example of a Path that can be animated:

<Path x:Name="MyPath" Fill="#FFA30000" Stroke="Black" Width="100" Height="100">
    <Path.Data>
        <PathGeometry FillRule="EvenOdd">
            <PathFigure IsClosed="True" StartPoint="0,0">
                <LineSegment Point="0,100"/>
                <LineSegment Point="100,100"/>
                <LineSegment Point="100,0"/>
            </PathFigure>
        </PathGeometry>
    </Path.Data>
</Path>

This path is a simple square and looks like this:

Now, let’s assume you want to recreate this programmatically using a collection of points that represent X,Y coordinates. If you’re using an ObservableCollection of Points (like I am) you can use the following method to return an the appropriate path.

Path createPath(ObservableCollection<Point> rawData)
{

    Path FinalPath = new Path();
    PathGeometry FinalPathGeometry = new PathGeometry();
    PathFigure PrimaryFigure = new PathFigure();

    //if you want the path to be a shape, you want to close the PathFigure
    //   that makes up the Path. If you want it to simply by a line, set
    //   PrimaryFigure.IsClosed = false;
    PrimaryFigure.IsClosed = true;
   
    PrimaryFigure.StartPoint = rawData[0];

    PathSegmentCollection LineSegmentCollection = new PathSegmentCollection();

    for (int i = 1; i < rawData.Count; i++)
    {
        LineSegment newSegment = new LineSegment();
        newSegment.Point = rawData[i];
        LineSegmentCollection.Add(newSegment);
    }

    PrimaryFigure.Segments = LineSegmentCollection;
    FinalPathGeometry.Figures.Add(PrimaryFigure);
    FinalPath.Data = FinalPathGeometry;

    return FinalPath;
}

Once you have the path in place, you can just add it to your layout and it should show up. If you’re still confused, you can download the project that I created this in and walk through the rest of it yourself.