Own WinForms Control Flickers and Has Bad Performance

Question

I have two problems with an own user control which uses bitmaps: - It flickers if it's redrawn via .NET's 'Refresh' method. - It has a bad performance. The control consists of three bitmaps: - A static background image. - A rotating rotor. - Another image depending on rotor angle. All used bitmaps have a resolution of 500x500 pixels. The control works like this: https://www.dropbox.com/s/t92gucestwdkx8z/StatorAndRotor.gif (it's a gif animation) The user control should draw itself everytime it gets a new rotor angle. Therefore, it has a public property 'RotorAngle' which looks like this: ``` public double RotorAngle { get { return mRotorAngle; } set { mRotorAngle = value; Refresh(); } } ``` `Refresh` raises the `Paint` event. The `OnPaint` event handler looks like this: ``` private void StatorAndRotor2_Paint(object sender, PaintEventArgs e) { // Draw the three bitmaps using a rotation matrix to rotate the rotor bitmap. Draw((float)mRotorAngle); } ``` But when I use this code - which wo…

Accepted Answer

First, per LarsTech's answer, you should use the `Graphics` context provided in the `PaintEventArgs`. By calling `CreateGraphics()` inside the `Paint` handler, you prevent `OptimizedDoubleBuffer` from working correctly.

Second, in your SetStyle block, add:

```
SetStyle( ControlStyles.Opaque, true );
```

... to prevent the base class Control from filling in the background color before calling your Paint handler.

I tested this in your example project, it seemed to eliminate the flickering.

Own WinForms Control Flickers and Has Bad Performance

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