What are the side effects of Control.Controls.Add in Winforms?

I am trying to dynamically create a rather large TableLayoutPanel for an application I'm working on. As I've read from other questions, the TableLayoutPanel class suffers from significant performance problems when handling large and changing contents; I have, however, come too far to switch to something else just now.

I have been able to get around most of the issues by suspending layout before adding controls to the individual cells. One problem remains - when the table is first shown, it appears to take a little开发者_运维知识库 time before the background colors (just white) and everything else ready to be shown - like just a little less than a second of ugliness. I have tried doing all layout on startup, so that no calculations remain when the control is finally added, but the first drawing of it remains ugly. The weird thing is that when the control is shown again later (I keep it in memory instead of recreating it all the time) after having been removed from the main form for a while, it appears right away without any layouting. This leads me to believe that something happens when I first add the control to a child control of the main form, something I haven't reproduced in my own layouting - the question is, what? In order to force layout of the control right after its initialization, but before it is first shown, I do the following:

table.SuspendLayout();
// Create a whole lot of controls here and add them to the TableLayoutPanel
table.ResumeLayout();
table.Size = reportControl.Panel2.ClientSize;
table.PerformLayout();
table.SuspendLayout();
// Add the TableLayoutPanel to the main form here

Shouldn't that be enough? Unless I am very much mistaken, I do not touch the TableLayoutPanel between this code block and when it is added to the main form. Still, when it is first added, it looks way different than the second time. Oh, and the TableLayoutPanel is double buffered, so that's not it I think.

The extra thing that happens when you call Controls.Add() is that the native Windows window gets created. Plus the windows for all the controls you put in the panel. Which tends to be slow because TLP is often stuffed to the gills with controls. This doesn't happen when you Remove() the control and don't Dispose() it.

You can create the window early by calling CreateControl(). It will take just as long, but maybe isn't as noticeable.