Avoid Flickering in Windows Forms?

Question

Double buffering not working with combo-box. is there any another methods to avoid flickering in windows forms?

i have one windows form with number of panels in it.

Answer 1

Yet another solution:

//TODO: Don't forget to include using System.Runtime.InteropServices.

internal static class NativeWinAPI
{
    internal static readonly int GWL_EXSTYLE = -20;
    internal static readonly int WS_EX_COMPOSITED = 0x02000000;

    [DllImport("user32")]
    internal static extern int GetWindowLong(IntPtr hWnd, int nIndex);

    [DllImport("user32")]
    internal static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);
}

And your form constructor should look as follows:

public MyForm()
{
    InitializeComponent();

    int style = NativeWinAPI.GetWindowLong(this.Handle, NativeWinAPI.GWL_EXSTYLE);
    style |= NativeWinAPI.WS_EX_COMPOSITED;
    NativeWinAPI.SetWindowLong(this.Handle, NativeWinAPI.GWL_EXSTYLE, style);
}

In the code above, you might change this.Handle to something like MyFlickeringPanel.Handle

You can read a bit more about it here: Extended Window Styles and here: CreateWindowEx.

With WS_EX_COMPOSITED set, all descendants of a window get bottom-to-top painting order using double-buffering. Bottom-to-top painting order allows a descendent window to have translucency (alpha) and transparency (color-key) effects, but only if the descendent window also has the WS_EX_TRANSPARENT bit set. Double-buffering allows the window and its descendents to be painted without flicker.

Answer 2

    protected override CreateParams CreateParams
    {
        get
        {
            CreateParams handleParam = base.CreateParams;
            handleParam.ExStyle |= 0x02000000;   // WS_EX_COMPOSITED       
            return handleParam;
        }
    }

Answer 3

Solution #1:
Use ComboxBox.BeginUpdate() before you add items. This will prevent the Control from repainting the ComboBox each time an item is added to the list. After adding the items, you can use ComboBox.EndUpdate() to repaint.

Solution #2

private void EnableDoubleBuffering()
{
    this.SetStyle(ControlStyles.OptimizedDoubleBuffer | ControlStyles.UserPaint | ControlStyles.AllPaintingInWmPaint, true);
}