Don’t forget to call your base
I’m working on a windows forms app in my spare time, and I just ran into this very frustrating issue.
I have a SplitContainer on the main form to divide my form. I wanted the SplitContainer to resize with the form so that when you resize the form, the form elements would also stretch and shrink. I had set the SplitContainer’s Dock to DockStyle.Fill (which is all I usually have to do) but the damn thing just would NOT resize. I had also set one of the panels in the SplitContainer to be fixed, so I thought that may be causing the issue, I also read on msdn that the docking respects the z-order of the controls and since I had added the SplitContainer after the other controls, I figured that may have something to do with it as well.
I easily created a new blank form with a SplitContainer and set that one to fill (even with a fixed panel) and it worked like a charm, argh! To open this test form I just added some code to my main form’s OnLoad method to show my blank test form. Right below my OnLoad method was the OnResize method. When I minimize my app, I want it to show up in the system tray, but not the taskbar, so here was my code for OnResize:
protected override void OnResize(EventArgs e)
{
if (WindowState == FormWindowState.Minimized)
Hide();
}
I realized I wasn’t calling base.OnResize(e). I added that line, voila! My docking now worked as expected 
