System.Windows.Controls.SelectionMultiple.SelectFromKey C# (CSharp) Method

        private bool SelectFromKey(MultiSelectTreeViewItem item)
        {
            if (item == null)
            {
                return false;
            }

            // If Ctrl is pressed just focus it, so it can be selected by Space. Otherwise select it.
            if (IsControlKeyDown)
            {
                FocusHelper.Focus(item, true);
                return true;
            }
            else
            {
                return SelectCore(item);
            }
        }