Undoable interactive actions and programmatic commands that can be carried out by WpfDiagram are represented by Command subclasses. The Command class provides the necessary interface to Execute, Undo or Redo actions. In some cases you will have to implement these methods in derived classes, but you must not call them directly. Use the Undo or Redo methods of the UndoManager to undo or redo a command. The UndoManager methods call the respective Command methods and in addition update the state of the command history and the Diagram.

The following WpfDiagram classes are derived from Command:

Command	Description
AddItemCmd	Adds a new item to the diagram.
RemoveItemCmd	Removes an item from the diagram.
AddGroupCmd	Creates a new hierarchical group.
RemoveGroupCmd	Destroys a group.
GroupAttachCmd	Attaches an item to a group.
GroupDetachCmd	Detaches an item from a group.
ModifyItemCmd	Moves or resizes an item.
RedimTableCmd	Change number of table's columns or rows.
ExpandItemCmd	Expands or collapses a tree of items.
ScrollTableCmd	Scrolls table's rows.
ExpandHeaderRowCmd	Expands or collapses tables sections.
ChangeItemCmd	Handles undo/redo of item property changes.
CompositeCmd	Allows several actions to be undo and redone at the same time.

Instances of most of these classes are created implicitly by WpfDiagram in response to users' actions or method calls. You might need to explicitly instantiate only ChangeItemCmd - to undo or redo property changes - and CompositeCmd - to present several actions as single undoable operation.

The data of your application might be tightly integrated in WpfDiagram diagrams, for example by Tag objects or .NET controls embedded in ControlNode items. In these cases WpfDiagram cannot detect, undo or redo changes to your data. To enable undo of such changes, you must inherit the Command class and implement your versions of the Execute, Undo and Redo methods. To record your own action in the undo/redo history, call the ExecuteCommand method of the Diagram class.