How to avoid flickering when a MDI child form is shown in C# Windows forms?

Question

When connected to RDC , Iam observing flickering issues for the background images of mdi child forms. How can I avoid them?

Answer 1

I am using this code, no flicker at all.

if (!CheckForm(childForm))
        {
            childForm.WindowState = FormWindowState.Minimized; //avoid flickering
            childForm.Show();
            childForm.WindowState = FormWindowState.Normal;
        }
        else
        {
            childForm.BringToFront();
            childForm.WindowState = FormWindowState.Minimized;
            childForm.Activate();
            childForm.WindowState = FormWindowState.Normal;
        }

Answer 2

I know this is a very late answer, but since all answers here (including the accepted) did not do anything against the flickering, I still like to post what did it for me

first of all, I had to do this

protected override CreateParams CreateParams
{
    get
    {
        CreateParams cp = base.CreateParams;

        // reduce flickering when switching mdi child forms (see also WndProc)
        cp.ExStyle |= 0x02000000; // Turn on WS_EX_COMPOSITED (which is essentially double buffered)

        return cp;
    }
}

But this is not enough, I also had to do this :

protected override void WndProc(ref Message msg)
{
    const int WM_NCPAINT = 0x85;
    const int WM_SIZE = 0x05;

    // reduce flickering when switching mdi child forms (see also CreateParams)
    if (msg.Msg == WM_NCPAINT)
    {
        if (this.WindowState == FormWindowState.Maximized)
            return;
    }

    // reduce flickering when switching mdi child forms (see also CreateParams)
    if (msg.Msg == WM_SIZE)
    {
        if (this.WindowState == FormWindowState.Maximized)
            return;
    }

    base.WndProc(ref msg);
}

I had read somewhere that I could achive all this by simply doing this :

this.SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);

But the flickering only gets worse when I do that.

Anyway, with this solution (at least in my mdi project) I have completely eliminated the flickering when switching between mdi child forms.
Hope this can help anyone looking for this problem.

Answer 3

Have you tried the following?

this.DoubleBuffered = true;

Put this in the constructor after the InitializeComponent.

Answer 4

I have been also struggling with same problem and didn't find anything what works including form.DoubleBuffered = true. So this is what works for me

form.WindowState = FormWindowState.Minimized;
form.Show();
form.WindowState = FormWindowState.Maximized;

On the designer side, leave the form window state to Normal.

Answer 5

I also faced this issue for a long time. And I just got this way to come out. Opening forms in Fill Dock mode instead of Maximized.

//childFrm.WindowState = FormWindowState.Maximized;
childFrm.Dock = DockStyle.Fill;

Remove any background image in MDI form.