public async Task SetSelectedIndex(int index)
        {
            CompletionListControl.SelectedIndex = index;
            CompletionListControl.InvalidateVisual();

            if (!UpdatingItems && CompletionListControl.SelectedIndex >= 0)
            {
                if (!CompletionListControl.Hidden[CompletionListControl.SelectedIndex])
                {
                    CompletionItem item = CompletionListControl.Items[CompletionListControl.SelectedIndex].item;
                    await GetSymbolComments(item);
                }
                else
                {
                    this.FindControl <Border>("DocumentationBorder").IsVisible = false;
                    await UpdateScrollViewer();
                }
            }
        }