The LVM_SETITEMCOUNT message prepares a list view control for adding a large number of items. You can send this message explicitly or by using the ListView_SetItemCount macro.
LVM_SETITEMCOUNT
wParam = (WPARAM) (int) cItems;
lParam = 0;
Parameters
cItems
Number of items that the list view control will ultimately contain.
Return Values
No return value.
Remarks
By sending the LVM_SETITEMCOUNT message before adding a large number of items, you enable a list view control to reallocate its internal data structures only once rather than every time you add an item.
See Also