Microsoft.Silverlight.Testing.Controls.TreeViewItem.OnKeyDown C# (CSharp) Method

        protected override void OnKeyDown(KeyEventArgs e)
        {
            base.OnKeyDown(e);

            if (Interaction.AllowKeyDown(e))
            {
                if (e.Handled)
                {
                    return;
                }

                // We ignore the Control modifier key because it is used
                // specifically for scrolling which is implemented in the
                // TreeView. We do not mark the event handled if Control is
                // pressed so that it will bubble up to the parent TreeView of
                // this item.
                switch (e.Key)
                {
                    // WPF merges the behavior for the Left and Right keys
                    // because they behave logically with respect to flow
                    // direction (which isn't available in Silverlight)
                    case Key.Left:
                        // The Left key will collapse an expanded item or
                        // move to the parent if the item is already
                        // collapsed.
                        if (!TreeView.IsControlKeyDown && CanExpandOnInput && IsExpanded)
                        {
                            if (FocusManager.GetFocusedElement() != this)
                            {
                                Focus();
                            }
                            else
                            {
                                IsExpanded = false;
                            }
                            e.Handled = true;
                        }
                        break;
                    case Key.Right:
                        // The Right key is only useful when the item has
                        // children
                        if (!TreeView.IsControlKeyDown && CanExpandOnInput)
                        {
                            // Expand the item if it is collapsed or move into
                            // the first child if it is already expanded.
                            if (!IsExpanded)
                            {
                                UserInitiatedExpansion = true;
                                IsExpanded = true;
                                e.Handled = true;
                            }
                            else if (HandleDownKey())
                            {
                                e.Handled = true;
                            }
                        }
                        break;
                    case Key.Up:
                        if (!TreeView.IsControlKeyDown && HandleUpKey())
                        {
                            e.Handled = true;
                        }
                        break;
                    case Key.Down:
                        if (!TreeView.IsControlKeyDown && HandleDownKey())
                        {
                            e.Handled = true;
                        }
                        break;
                    case Key.Add:
                        if (CanExpandOnInput && !IsExpanded)
                        {
                            UserInitiatedExpansion = true;
                            IsExpanded = true;
                            e.Handled = true;
                        }
                        break;
                    case Key.Subtract:
                        if (CanExpandOnInput && IsExpanded)
                        {
                            IsExpanded = false;
                            e.Handled = true;
                        }
                        break;
                }
            }

            // Because Silverlight's ScrollViewer swallows many useful key
            // events (which it can ignore on WPF if you override
            // HandlesScrolling or use an internal only variable in
            // Silverlight), the root TreeViewItems explicitly propagate KeyDown
            // events to their parent TreeView.
            if (IsRoot)
            {
                TreeView parent = ParentTreeView;
                if (parent != null)
                {
                    parent.PropagateKeyDown(e);
                }
            }
        }