Flickering in a Windows Forms app

Try the following code. This should go in the main form and any other custom user controls you have.

        // Enable double duffering to stop flickering.
        this.SetStyle(ControlStyles.DoubleBuffer, true);
        this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
        this.SetStyle(ControlStyles.UserPaint, true);
        this.SetStyle(ControlStyles.SupportsTransparentBackColor, false);
        this.SetStyle(ControlStyles.Opaque, false);
        this.SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
        this.SetStyle(ControlStyles.ResizeRedraw, true);

I figured it out. The trick is to remove the WS_EX_COMPOSITED flag after the form is shown. The full explanation and code at my blog:

How to get rid of flicker on Windows Forms applications

I know this question is a little old, but better late than never. I used your original example you linked to come up with one that toggles it on when resizing, then toggles it back off to draw everything else perfectly. Hopefully it helps others searching for a solution to this problem. As the OP knows, DoubleBuffering alone properties don't solve flickering issues.

Here's a work-around to stop flickering when a user resizes a form, but without messing up the drawing of controls such as DataGridView, NumericUpDown, etc. Provided your form name is "Form1":

int intOriginalExStyle = -1;
bool bEnableAntiFlicker = true;

public Form1()
{
    ToggleAntiFlicker(false);
    InitializeComponent();
    this.ResizeBegin += new EventHandler(Form1_ResizeBegin);
    this.ResizeEnd += new EventHandler(Form1_ResizeEnd);
}

protected override CreateParams CreateParams
{
    get
    {
        if (intOriginalExStyle == -1)
        {
            intOriginalExStyle = base.CreateParams.ExStyle;
        }
        CreateParams cp = base.CreateParams;

        if (bEnableAntiFlicker)
        {
            cp.ExStyle |= 0x02000000; //WS_EX_COMPOSITED
        }
        else
        {
            cp.ExStyle = intOriginalExStyle;
        }

        return cp;
    }
} 

private void Form1_ResizeBegin(object sender, EventArgs e)
{
    ToggleAntiFlicker(true);
}

private void Form1_ResizeEnd(object sender, EventArgs e)
{
    ToggleAntiFlicker(false);
}

private void ToggleAntiFlicker(bool Enable)
{
    bEnableAntiFlicker = Enable;
    //hacky, but works
    this.MaximizeBox = true;
}