Suspend Redraw of Windows Form

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.

---

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...
}