Question

I have a windows form. It contains several datagridviews on it. At some point, the user can press a button which updates the datagridviews. When they do, they can usually sit and watch the datagridview redraw itself, one row at a time. I’d like for the control to not paint until its ‘done’, that is, I’d like a way to tell the control to

Control.SuspendRedraw() this.doStuff() this.doOtherStuff() this.doSomeReallyCoolStuff() Control.ResumeRedaw() 

I’ve seen the SuspendLayout / ResumeLayout functions, but they do nothing (they seem to be more related to resizing/moving controls, not just editting their datavalues?)

Answer 1

There are a couple of things that you can try:

First, try setting the DoubleBuffer property of the DataGridView to true. This is the property on the actual DataGridView instance, not the Form. It’s a protected property, so you’ll have to sub-class your grid to set it.

class CustomDataGridView: DataGridView {     public CustomDataGridView()     {         DoubleBuffered = true;     }  } 

I’ve seen a lot of small draw updates take a while with the DataGridView on some video cards, and this may solve your problem by batching them up before they are sent off for display.

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Another thing you can try is the Win32 message WM_SETREDRAW

// ... this would be defined in some reasonable location ...  [DllImport('user32.dll', CharSet = CharSet.Auto, SetLastError = false)] static extern IntPtr SendMessage(HandleRef hWnd, Int32 Msg, IntPtr wParam, IntPtr lParam);  static void EnableRepaint(HandleRef handle, bool enable) {     const int WM_SETREDRAW = 0x000B;     SendMessage(handle, WM_SETREDRAW, new IntPtr(enable ? 1 : 0), IntPtr.Zero); } 

Elsewhere in your code you’d have

HandleRef gh = new HandleRef(this.Grid, this.Grid.Handle); EnableRepaint(gh, false); try {     this.doStuff();     this.doOtherStuff();     this.doSomeReallyCoolStuff(); } finally {     EnableRepaint(gh, true);     this.Grid.Invalidate(); // we need at least one repaint to happen... }