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Editorial Team
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Asked: 2026-06-02T11:14:39+00:00

I have an application drawing a lot of small rectangles (about 1 million) using

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I have an application drawing a lot of small rectangles (about 1 million) using GDI+ in C# and the performance is… not so good. I understand that constructing a lot of Rectangle objects for passing them to Graphis.FillRectangle takes some time. I also understand that I cannot avoid this if the Rectangles change from from frame to frame, because Rectangle is designed to be immutable. My question therefore is: is there any possibility to improve the performance of this drawing call except if all Rectangles must be assumed to be visible?

Thanks in advance,
Christoph

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1 Answer

  1. Editorial Team

    I suggest you use the array variant of the call instead:

    FillRectangles(Brush brush, Rectangle[] rects);

    If that does not work for you because you need different brushes or the like, you should group the primitives by state (brush) and draw the arrays each in a single go. A quick test shows at least three times the performance, i.e. 300K Rectangles drawn individually feel about as choppy as 1M Rectangles drawn in one go.

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