In your RetrieveVirtualItem section you mention that the if block should never be called, but you’ve seen it once during debugging – using the scroll wheel on a mouse I see this block hit multiple times.

Rich

Another thing that we have encountered in virtual mode is that for large numbers of records, where there is a considerable perf hit to retrieving even just a subset of the records, the ListView scrolling behaviour makes the list less usable.

While WPF has deferred scrolling behaviour, this isn’t available by default (at least not that I could find) in the WinForms listview.

A bit of a hack, but thanks to http://www.microsoft.com/msj/1299/c/c1299.aspx I was able to cook something up that makes the WinForms listview also use “deferred” scrolling behaviour (e.g. only when the thumb is released, does the scroll happen), which has improved the user experience immensely.

Here’s the code (no idea how it’s going to render as a comment though):

public class DeferredScrollingListView : System.Windows.Forms.ListView
{
const int WM_VSCROLL=0×0115;
const int SB_THUMBPOSITION=0×4;
const int SB_THUMBTRACK=0×5;

protected override void WndProc(ref System.Windows.Forms.Message m)
{
if( m.Msg==WM_VSCROLL )
{
int wParam=m.WParam.ToInt32();
if( ((short)wParam)==SB_THUMBTRACK )
{
if( ignoreThumbTracks_ )
{
return;
}
}
else if( ((short)wParam)==SB_THUMBPOSITION )
{
ignoreThumbTracks_=false;
SendMessage(m.HWnd,WM_VSCROLL,MakeWParam(SB_THUMBTRACK,((short)wParam<<16)),m.LParam);
ignoreThumbTracks_=true;
}
}

base.WndProc(ref m);
}

[DllImport("user32.dll",CharSet=CharSet.Auto)]
static extern IntPtr SendMessage(IntPtr hWnd,int msg,IntPtr wParam,IntPtr lParam);

static IntPtr MakeWParam(int loWord,int hiWord)
{
return new IntPtr((loWord&0xFFFF)+((hiWord&0xFFFF)<<16));
}

bool ignoreThumbTracks_=true;
}

Interesting article, FYI I coordinate an open source project on CodePlex called Supelist which is a outlook style list view you might be interested at looking at.

http://www.CodePlex.com/Superlist

Carry on with the good work

Regards
Lee