OleUndoEngine Class

Artikel
10/27/2012

Provides a default implementation of undo management for designers.

Inheritance Hierarchy

System.Object
System.ComponentModel.Design.UndoEngine
Microsoft.VisualStudio.Shell.Design.OleUndoEngine

Namespace: Microsoft.VisualStudio.Shell.Design
Assembly: Microsoft.VisualStudio.Shell.Design (in Microsoft.VisualStudio.Shell.Design.dll)

Syntax

'Declaration
Public Class OleUndoEngine _
    Inherits UndoEngine _
    Implements IVsLinkedUndoClient

public class OleUndoEngine : UndoEngine, 
    IVsLinkedUndoClient

The OleUndoEngine type exposes the following members.

Constructors

	Name	Description
	OleUndoEngine	Initializes a new instance of OleUndoEngine.

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Properties

	Name	Description
	Enabled	Enables or disables the UndoEngine. (Inherited from UndoEngine.)
	UndoInProgress	Indicates if an undo action is in progress. (Inherited from UndoEngine.)

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Methods

	Name	Description
	AddUndoUnit	Adds the undo unit to the undo unit manager. (Overrides UndoEngine.AddUndoUnit(UndoEngine.UndoUnit).)
	CreateUndoUnit	Creates a new undo unit. (Overrides UndoEngine.CreateUndoUnit(String, Boolean).)
	DiscardUndoUnit	Closes this unit if it is a parent undo unit. (Overrides UndoEngine.DiscardUndoUnit(UndoEngine.UndoUnit).)
	Dispose()	Releases all resources used by the UndoEngine. (Inherited from UndoEngine.)
	Dispose(Boolean)	Disposes the resources of this object. (Overrides UndoEngine.Dispose(Boolean).)
	Equals	Determines whether the specified object is equal to the current object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetRequiredService	Gets the requested service. (Inherited from UndoEngine.)
	GetService	Gets the requested service. (Inherited from UndoEngine.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	OnUndoing	Raises the Undoing event. (Inherited from UndoEngine.)
	OnUndone	Raises the Undone event. (Inherited from UndoEngine.)
	ToString	Returns a string that represents the current object. (Inherited from Object.)

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Events

	Name	Description
	Undoing	Occurs immediately before an undo action is performed. (Inherited from UndoEngine.)
	Undone	Occurs immediately after an undo action is performed. (Inherited from UndoEngine.)

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Explicit Interface Implementations

	Name	Description
	IVsLinkedUndoClient.OnInterveningUnitBlockingLinkedUndo	Indicates that the undo manager is blocking another undo manager from executing a linked action.

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Remarks

The OleUndoEngine class provides a default implementation of the UndoEngine and IVsLinkedUndoClient interfaces used to manage undo operations, which allow users to reverse their recent changes when modifying a code element.

Note

Typically, designers implemented under Visual Studio and .NET Framework are based on Control and have undo support automatically provided by the environment.

Designers will need to implement their own undo management if either:

The designer uses a graphical user interface, referred to as a ViewAdapter, other than that supplied by Control.

This will require the registry of the ViewAdapter with Visual Studio using ProvideViewAdapterAttribute.

An example of this might be creating a product with a web-based graphical design interface rather than a .NET Framework based graphical interface.
The designers do not use the Visual Studio code generation model provided in the System.CodeDom name space.

The OleUndoEngine class transparently supports child undo units, as it uses custom undo units (atomic sections of code which can be removed in an undo operation) UndoEngine.UndoUnit, which fully implement IOleUndoUnit and IOleParentUndoUnit.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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