System.Windows.Controls.MultiSelectTreeViewItem.OnKeyDown C# (CSharp) Method

        protected override void OnKeyDown(KeyEventArgs e)
        {
            base.OnKeyDown(e);
            if (!e.Handled)
            {
                Key key = e.Key;
                switch (key)
                {
                    case Key.Left:
                        if (IsExpanded)
                        {
                            IsExpanded = false;
                        }
                        else
                        {
                            ParentTreeView.Selection.SelectParentFromKey();
                        }
                        e.Handled = true;
                        break;
                    case Key.Right:
                        if (CanExpand)
                        {
                            if (!IsExpanded)
                            {
                                IsExpanded = true;
                            }
                            else
                            {
                                ParentTreeView.Selection.SelectNextFromKey();
                            }
                        }
                        e.Handled = true;
                        break;
                    case Key.Up:
                        ParentTreeView.Selection.SelectPreviousFromKey();
                        e.Handled = true;
                        break;
                    case Key.Down:
                        ParentTreeView.Selection.SelectNextFromKey();
                        e.Handled = true;
                        break;
                    case Key.Home:
                        ParentTreeView.Selection.SelectFirstFromKey();
                        e.Handled = true;
                        break;
                    case Key.End:
                        ParentTreeView.Selection.SelectLastFromKey();
                        e.Handled = true;
                        break;
                    case Key.PageUp:
                        ParentTreeView.Selection.SelectPageUpFromKey();
                        e.Handled = true;
                        break;
                    case Key.PageDown:
                        ParentTreeView.Selection.SelectPageDownFromKey();
                        e.Handled = true;
                        break;
                    case Key.A:
                        if (e.KeyboardDevice.Modifiers == ModifierKeys.Control)
                        {
                            ParentTreeView.Selection.SelectAllFromKey();
                            e.Handled = true;
                        }
                        break;
                    case Key.Add:
                        if (CanExpandOnInput && !IsExpanded)
                        {
                            IsExpanded = true;
                        }
                        e.Handled = true;
                        break;
                    case Key.Subtract:
                        if (CanExpandOnInput && IsExpanded)
                        {
                            IsExpanded = false;
                        }
                        e.Handled = true;
                        break;
                    case Key.F2:
                        if (ParentTreeView.AllowEditItems && ContentTemplateEdit != null && IsFocused && IsEditable)
                        {
                            IsEditing = true;
                        }
                        e.Handled = true;
                        break;
                    case Key.Escape:
                        StopEditing();
                        e.Handled = true;
                        break;
                    case Key.Return:
                        FocusHelper.Focus(this, true);
                        IsEditing = false;
                        e.Handled = true;
                        break;
                    case Key.Space:
                        ParentTreeView.Selection.SelectCurrentBySpace();
                        e.Handled = true;
                        break;
                }
            }
        }