Imagine the following scenario:

this.SetStyle(ControlStyles.UserPaint, true); //this doesn’t change anything

…

void OpenSomeForm()
{
    SomeForm sf = new SomeForm();
    sf.SomeEvent += new … (SomeEventOcurred);
    sf.ShowDialog();
}

private void SomeEventOcurred(…)
{
    OnePanelInThisForm.Invalidate();
}

private void OnePanelInThisForm_Paint(object sender, PaintEventArgs e)
{
     DoSomeDrawing(e.Graphics);
}

Now, OnePanelInThisForm draws correctly when the form loads. But if SomeEventOcurred is Fired from “SomeForm”, the paint event is not fired. If I close and reopen the form it correctly repaints. If I add a button to the form that executes: OnePanelInThisForm.Invalidate(); the panel is correctly repaint.

What am I missing?