Specifies generic undo/redo functionality at design time.
Assembly: System.Design (in System.Design.dll)
The abstract class provides a default implementation of undo functionality at design time. An undo unit represents a single unit of undoable work. This unit is added to a stack and the user can then walk the stack to undo each action. Undo units typically are designed to toggle, which means that calling undo twice returns the application to its starting state.
The class takes advantage of the following characteristics of objects running within the designer:
All interesting objects can be persisted to some format by the designer loader.
All objects raise property-change notifications when a property is changed.
IDesignerHost offers the idea of transactions, which can be used to fabricate an undo action that spans multiple smaller actions.
With these features, can fabricate any undo units it needs automatically.
Do not change property values directly. The class requires you to use the appropriate TypeDescriptor to change property values.
monitors for change notifications to create undo units, and the units themselves consist of serialized object states. The following table shows the services that must be available when is created.
Saves property and object values for a component before and after a change is made.
Notifies the undo engine of changes made to components.
Used to track transactions.
The undo engine tracks transactions and creates a single undo unit that encompasses a transaction. As a result, the undo engine has control over the duration of an undoable action. Also, because transactions can be named, undoable actions inherit their names from the current transaction. If no transaction is available and a change is reported, the undo engine creates an undo name based on the type of change (for example, "Change property 'Text'").
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.