How to keep rectangle on desktop

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Hello, I have draw Rectangle on Desktop but now I have some Problems with ths.
It is desapearing when I refresh desktop or moving above some window. I need do have this Rectangle on Desktop until I Press some Button(for example Refresh Button).

What I have tried:

So, I am drawing Rectangle on Desktop with following code:

C#

Pen pen = new Pen(Color.Yellow, 2);
            IntPtr desktop = GetDC(IntPtr.Zero);
            using (Graphics g = Graphics.FromHdc(desktop))
            {
                g.DrawRectangle(pen, x, y, width, height);
            }
            ReleaseDC(IntPtr.Zero, desktop);

Posted 10-Jul-16 2:12am

dave_bulac

Updated 11-Jul-16 14:23pm

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[no name] 10-Jul-16 8:20am

You should create a transparent window without border, for which you set "Parent" to the desktop. This will receive then the WM_PAINT Messages where you can refresh the rectangle.

dave_bulac 10-Jul-16 8:30am

what do you mean "for which you set "Parent" to the desktop" ?

[no name] 10-Jul-16 8:57am

Have a look here, code snippet at bottom:
Create Transparent Overlay on Desktop - Software Development | DaniWeb[^]

BillWoodruff 12-Jul-16 6:20am

It would be interesting to know the purpose, the reason, why you want to do this, and knowing that might assist us to assist you.

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OriginalGriff · Answer 1 · 2016-07-10T03:09:00

Drawing anything in Windows ia transitory, unless it is drawn onto the surface of a bitmap or similar that is redrawn when necessary. As a result, if you don't re-draw your rectangle when another app covers it up and then it becomes visible again it will disappear - there really isn't anything you can do about that.

And your app doesn't "own" the desktop, so there is no mechanism for your app to be notified that your rectangle needs re-drawing.
You could do it with a Timer - but that's a messy and nasty kludge - but other than that, you can copy the desktop, create a temporary wallpaper and draw on that so the system "maintains" your drawing for you.
This may help: c# - Change desktop wallpaper using code in .NET - Stack Overflow[^]