Restoring WinForm with textbox containing large amount of data

Question

I have created a form in C# (VS2010) which contain (among other) a textbox control. The textbox may contain large amount of data at some point (~3 million chars).

When scrolling or moving the form around no problems are encountered, but when the form is minimized and restored back again, a repaint sequence (I believe) is triggered which causes a big lag of around 5-10 seconds for the form to be repainted.

I've already tried several solutions:

1. Using double buffer – according to what I've read, double buffering applies only to the form itself and not to its controls

   this.SetStyle(ControlStyles.DoubleBuffer, true); this.SetStyle(ControlStyles.AllPaintingInWmPaint, true); this.SetStyle(ControlStyles.UserPaint, true);

2. Disabling the textbox redrew once minimized using: SendMessage(this.my_textBox.Handle, WM_SETREDRAW, false, 0); and enabling back after form is restored. I've noticed that the form repaint lag exist also if I don't re-enable the textbox repaint.

3. Manual double buffer using a bitmap – similar results as #1.

I read somewhere that this issue might be related to the textbox control trying to shrink or adjust to the amount of data, but couldn't override it.

I previously had the same project in MFC, but didn't encounter any repaint or lagging issues there.

Please advise me how to solve this issue.

Answer 1

Found the problem!!! Issue was related to the textbox Anchor property. once i removed it, window restore was immediate. BTW, the new custom class isn't required