public void GetItemInGroup(int groupIndex, int n, out int itemIndex) {
if (this._VirtualListView.Groups == null || this._VirtualListView.Groups.Count == 0) {
itemIndex = -1;
return;
}
var group = this._VirtualListView.Groups.SingleOrDefault(w => w.Index == groupIndex);
if (group == null) {
itemIndex = -1;
return;
}
var itemInGroup = group.Items[n];
itemIndex = itemInGroup.ItemIndex;
}