equivalent CreateGraphics in wpf

Question

So, I've used winForms .CreateGraphics to draw a variety of different things, from lines to boxes to images. It was very snappy and responsive.

I am trying to learn WPF in C#

I found that WPF allows me to "add" rectangle objects to a canvas which will display them properly. HOWEVER, I am drawing hundreds of thousands of rectangles at times, and the draw rate can become exceedingly slow, and the UI becomes less snappy when I move even 1 of the rectangles.

Painting directly onto an element in winForms was not very fast, but it was consistent regardless of how much I painted.

Is there a similar solution to doing this in WPF?

I tried adding a linq to System.Drawing, which gave me a Graphics object, but none of the wpf elements i tried have the .CreateGraphics() method.

Answer 1

You would need to create a control that overrides OnRender and do your drawing in there. There isn't a way for you to draw onto another control, but a control can draw itself.

Also, keep in mind that WPF uses retained graphics, so if you change something you need to invalidate the visual as needed.

EDIT:

Something like:

public class MyControl : Control {

    public MyControl() {
       this.Rects = new ObservableCollection<Rect>();
       // TODO: attach to CollectionChanged to know when to invalidate visual
    }

    public ObservableCollection<Rect> Rects { get; private set; }

    protected override void OnRender(DrawingContext dc) {
        SolidColorBrush mySolidColorBrush  = new SolidColorBrush();
        mySolidColorBrush.Color = Colors.LimeGreen;
        Pen myPen = new Pen(Brushes.Blue, 10);

        foreach (Rect rect in this.Rects)
            dc.DrawRectangle(mySolidColorBrush, myPen, rect);
    }
}