Is SuspendLayout/ResumeLayout worthless or am I going about it wrong?

Question

I have two tab pages hosting TableLayoutPanels that I dynamically populate with labels and textboxes. The first one gets 96 labels and 96 textboxes, and its flicker is acceptable/tolerable, so I didn't bother to add a SuspendLayout/ResumeLayout pair.

However, the second one gets 96 labels and 288 textboxes, and its painting/flickering is intolerable. IOW, 192 controls seems to be okay, but 384 is decidedly not.

I was calling SuspendLayout prior to creating the controls dynamically, and then ResumeLayout in the finally block, but removed them, and voila! Like the first tabPage/TLP, the flicker is acceptable.

Why does this addition by subtraction work?

`SuspendLayout` is a method of the `Control` class. Which `Control` are you calling it on? — Robert Harvey, Aug 20 '12 at 23:13
Good tip; I was calling it on "this" (the form). So, I tried calling it on both the tabPage and the TableLayoutPanel. It doesn't seem to work any better/worse than commenting out the calls to this.SuspendLayout() and this.ResumeLayout() did. — B. Clay Shannon-B. Crow Raven, Aug 20 '12 at 23:27
Please review http://stackoverflow.com/questions/3718380/winforms-double-buffering — Robert Harvey, Aug 20 '12 at 23:34
I used that code of Passant's before, and it worked like a charm, but the powers that be didn't want to use it, thinking it was too arcane. — B. Clay Shannon-B. Crow Raven, Aug 21 '12 at 00:02
Also see [Prevent redrawing of controls on resize for Windows Forms](http://stackoverflow.com/a/8930446/719186). — LarsTech, Aug 21 '12 at 03:02
OK, that makes a lot of sense. "This code works, but we don't want to use it because we think its arcane." >_ — Robert Harvey, Aug 21 '12 at 14:47
I have tested SuspendLayout() with ScrollToCaret() and it produces flicker and does not suspend the layout. If your layout involves moving the scroll position, this method call will not actually suspend updating of the screen. — Dan, Mar 10 '19 at 17:47

score 10 · Accepted Answer · edited May 23 '17 at 12:30

You may also try the two methods, I have listed in this thread. Hope they are not too arcane:

https://stackoverflow.com/a/15020157/1307504

This methods really suspends and resumes the layout. But you should never forget to call EndControlUpdate().

I use this in any generically control I am creating. I tried a lot with alling suspend and resume layout. It never worked the way I thought it should.

score 2 · Answer 2 · edited Aug 18 '17 at 17:10

Initially, I had same doubt that does the SuspendLayout and ResumeLayout really works. Then I tried myself and created a sample application and got to know the concept much better later on.

So, here is what I did:

mainPanel.SuspendLayout()

create child control

call child.SuspendLayout()

change the child control properties

add the child control to the mainPanel

call child.ResumeLayout(false) - this means: next layout run, relayout this control, but not immediately

repeat (2-6) for every child-control

call mainPanel.ResumeLayout(true) - this means: relayout my mainPanel and every child-control now!

Also to Prove My Concept Here is the Sample Application

Stopwatch stopWatch = new Stopwatch();
        stopWatch.Start();

        this.SuspendLayout();
        for (int i = 0; i < 2000; i++)
        {
            var textbox = new TextBox();
            //textbox.SuspendLayout();
            //textbox.Dock = i% 2 ==0 ? DockStyle.Left : DockStyle.Right;
            textbox.Dock = DockStyle.Fill;
            textbox.Top = i * 10;
            textbox.Text = i.ToString();
            this.Controls.Add(textbox);
            //textbox.ResumeLayout(false);

        }
        stopWatch.Stop();
        TimeSpan ts = stopWatch.Elapsed;
        string elapsedTime = String.Format("{0:00}:{1:00}:{2:00}.{3:00}",ts.Hours, ts.Minutes, ts.Seconds,ts.Milliseconds / 10);

        this.ResumeLayout(true);
        MessageBox.Show(elapsedTime);

Don't Forget to Comment out this.SuspendLayout() and this.ResumeLayout(True) — Sandip, Aug 18 '17 at 16:50

Is SuspendLayout/ResumeLayout worthless or am I going about it wrong?

2 Answers2