取消选择一项时如何在 System.Windows.Forms.ListView 中选择其他项

Question

When you have multiple items selected in a ListView and you click one of the selected items, the default behavior is for all the other items to become deselected, leaving just the that was clicked selected. I'd like the exact inverse behavior: clicking one of the selected items deselects just that item and leaves the other items selected.

I've seen answers like this one and this one . The first is talking about preventing the mouse click from doing anything which isn't what I want obviously, and the second is about cancelling the index changing event. I tried adapting the latter for my needs, but it still results in the other items becoming deselected.

private void HandleIncludableFilesListViewSelectedIndexChanging
    (object sender, Controls.Events.ListViewItemChangingEventArgs e)
{
   if (_includableFilesListView.Items[e.Index].Selected) e.Cancel = true;
}

The above event handler only fires for the single item that is clicked on, and not for every other item as they're being deselected.

Is there some way to achieve this?

Answer 1

As an option you can override DefWndProc and handle WM_LBUTTONDOWN . Then do hit-test and check if the clicked point is an item, revert the Selected property of the item:

public class MyListView : ListView
{
    const int WM_LBUTTONDOWN = 0x0201;
    protected override void DefWndProc(ref Message m)
    {
        if (m.Msg == WM_LBUTTONDOWN)
        {
            int x = (m.LParam.ToInt32() & 0xffff);
            int y = (m.LParam.ToInt32() >> 16) & 0xffff;
            var item = this.HitTest(x, y).Item;
            if (item != null)
                item.Selected = !item.Selected;
            else
                base.DefWndProc(ref m);
        }
        else
        {
            base.DefWndProc(ref m);
        }
    }
}