Question

I have used the PAINT event to draw a wave on a Panel in Winows Form Application. But when using it WPF, I didn’t find any such element equivalent to a Panel which has a Paint Event. Googled a lot too but no great use.

Well, I need to draw a waveform in WPF so suggest appropriate solutions wrt PaintArgsEvent or a new solution altogether.

Thank You!

Answer 1

You are looking for the DrawingVisual Class

From first Link:

The DrawingVisual is a lightweight drawing class that is used to render shapes, images, or text. This class is considered lightweight because it does not provide layout or event handling, which improves its performance. For this reason, drawings are ideal for backgrounds and clip art.

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You also have access to a PolyLine Class that you can add a point Collection to. This example is a modified MSDN Forum example

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        float x0 = 100f;
        float y0 = 100f;
        Polyline myPoly = new Polyline();
        PointCollection polyPoints = myPoly.Points;
        Point[] points = new Point[200];

        for (int j = 0; j < 200; j++)
        {
            points[j] = new Point();
            points[j].X = x0 + j;
            points[j].Y = y0 -
            (float)(Math.Sin((2 * Math.PI * j) / 200) * (200 / (2 * Math.PI)));
        }

        for (int i = 0; i < points.Length ; i++)
        {
            polyPoints.Add(points[i]);
        }

        myPoly.Stroke = Brushes.Green;
        myPoly.StrokeThickness = 5;
        StackPanel mainPanel = new StackPanel();
        mainPanel.Children.Add(myPoly);
        this.Content = mainPanel;

    }
}

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And a Modified MSDN example:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        float x0 = 100f;
        float y0 = 100f;
        Point[] points = new Point[200];

        for (int j = 0; j < 200; j++)
        {
            points[j] = new Point();
            points[j].X = x0 + j;
            points[j].Y = y0 -
            (float)(Math.Sin((2 * Math.PI * j) / 200) * (200 / (2 * Math.PI)));
        }

        DrawingBrush db = new DrawingBrush(CreateDrawingVisualRectangle(points).Drawing);
        StackPanel mainPanel = new StackPanel();
        mainPanel.Background = db;
        this.Content = mainPanel;

    }

    private DrawingVisual CreateDrawingVisualRectangle( Point[] pointarray)
    {
        DrawingVisual drawingVisual = new DrawingVisual();

        // Retrieve the DrawingContext in order to create new drawing content.
        DrawingContext drawingContext = drawingVisual.RenderOpen();

       // Create a rectangle and draw it in the DrawingContext.
       for (int i = 0; i < pointarray.Length-1; i++)
       {
           drawingContext.DrawLine(new Pen(new SolidColorBrush(Colors.Blue), 2), pointarray[i], pointarray[i + 1]);
       }

       // Persist the drawing content.
       drawingContext.Close();

       return drawingVisual;
     }

}