UndoableObjectBase Class

public abstract class UndoableObjectBase : PersistableObjectBase, 
	ICanUndoRedo, ICanUndo, IRevertibleChangeTracking, IChangeTracking

Public MustInherit Class UndoableObjectBase
	Inherits PersistableObjectBase
	Implements ICanUndoRedo, ICanUndo, IRevertibleChangeTracking, IChangeTracking

public ref class UndoableObjectBase abstract : public PersistableObjectBase, 
	ICanUndoRedo, ICanUndo, IRevertibleChangeTracking, IChangeTracking

[<AbstractClassAttribute>]
type UndoableObjectBase =  
    class
        inherit PersistableObjectBase
        interface ICanUndoRedo
        interface ICanUndo
        interface IRevertibleChangeTracking
        interface IChangeTracking
    end

The UndoableObjectBase type exposes the following members.

	Name	Description
	UndoableObjectBase	Initializes a new instance of the UndoableObjectBase class

	Name	Description
	CanRedo	Gets whether there are changes to redo.
	CanUndo	Gets whether there are changes to undo.
	IsModified	Gets whether this instance has been modified. Modified state can be set by the SetModified method. (Inherited from ObservableObjectBase.)
	UndoCapacity	Gets or sets the undo capacity. Default value: 20.

	Name	Description
	AffectsModifiedState	Gets whether the change of the specified propertyName affects the IsModified property. The UndoableObjectBase implementation excludes the IsModified, UndoCapacity, CanUndo and CanRedo properties. (Overrides ObservableObjectBaseAffectsModifiedState(String).)
	CanGetProperty	Gets whether the specified property can be get. The base implementation allows to get the actual instance properties in this instance. (Inherited from ObservableObjectBase.)
	CanSetProperty	Gets whether the specified property can be set. The base implementation allows to set the actual instance properties in this instance if the specified value is compatible with the property type. (Inherited from ObservableObjectBase.)
	ClearUndoHistory	Clears the undo/redo history without performing any undo.
	Clone	Creates a new object that is a copy of the current instance. The base implementation clones the internal property storage, the IsModified property and if clonePropertyChanged is , then also the subscribers of the PropertyChanged event. (Inherited from ObservableObjectBase.)
	Dispose	Releases the resources held by this instance. (Inherited from ObservableObjectBase.)
	Dispose(Boolean)	Releases the resources held by this instance. The base implementation removes the subscribers of the PropertyChanged event. (Inherited from ObservableObjectBase.)
	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.)
	GetT(FuncT, String)	Gets the value of a property, or - if it was not set before -, then creates its initial value. The created initial value will be stored in the internal property storage without triggering the PropertyChanged event. For constant or simple expressions, or to return a default value for a non-existing property without storing it internally use the other Get overload. For an example, see the Remarks section of the ObservableObjectBase class. (Inherited from ObservableObjectBase.)
	GetT(T, String)	Gets the value of a property or defaultValue if no value is stored for it. No new value will be stored if the property does not exist. If the default initial value is too complex and should not be evaluated every time when the property is get, or to throw an exception for an uninitialized property use the other Get overload. For an example, see the Remarks section of the ObservableObjectBase class. (Inherited from ObservableObjectBase.)
	GetHashCode	Serves as the default hash function. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	OnPropertyChanged	Raises the PropertyChanged event. (Overrides ObservableObjectBaseOnPropertyChanged(PropertyChangedExtendedEventArgs).)
	RedoAll	Redoes all possible redo steps.
	ResetProperty	Resets the property of the specified name, meaning, it will be removed from the underlying storage so the getter methods will return the default value again. (Inherited from ObservableObjectBase.)
	ResumeChangedEvent	Resumes the raising of the PropertyChanged event suspended by the SuspendChangeEvents method. (Inherited from ObservableObjectBase.)
	Set	Sets the value of a property. For an example, see the Remarks section of the ObservableObjectBase class. (Inherited from ObservableObjectBase.)
	SetModified	Sets the modified state of this ObservableObjectBase instance represented by the IsModified property. (Inherited from ObservableObjectBase.)
	SuspendChangedEvent	Suspends the raising of the PropertyChanged event until ResumeChangeEvents method is called. Supports nested calls. (Inherited from ObservableObjectBase.)
	ToString	Returns a string that represents the current object. (Inherited from Object.)
	TryRedo	Tries to perform one redo step.
	TryUndo	Tries to perform one undo step.
	UndoAll	Undoes all possible undo steps.

	Name	Description
	PropertyChanged	Occurs when a property value changed. The actual type of the event argument is PropertyChangedExtendedEventArgs. (Inherited from ObservableObjectBase.)

	Name	Description
	Convert(Type, CultureInfo)	Overloaded. Converts an Object specified in the obj parameter to the desired targetType. See the Examples section of the generic ConvertTTarget(Object, CultureInfo) overload for an example. (Defined by ObjectExtensions.)
	ConvertTTarget(CultureInfo)	Overloaded. Converts an Object specified in the obj parameter to the desired TTarget. (Defined by ObjectExtensions.)
	In	Gets whether item is among the elements of set. See the Examples section of the generic InT(T, T) overload for an example. (Defined by ObjectExtensions.)
	TryConvert(Type, Object)	Overloaded. Tries to convert an Object specified in the obj parameter to the desired targetType. (Defined by ObjectExtensions.)
	TryConvert(Type, CultureInfo, Object)	Overloaded. Tries to convert an Object specified in the obj parameter to the desired targetType. (Defined by ObjectExtensions.)
	TryConvertTTarget(TTarget)	Overloaded. Tries to convert an Object specified in the obj parameter to the desired TTarget. See the Examples section of the ConvertTTarget(Object, CultureInfo) method for a related example. (Defined by ObjectExtensions.)
	TryConvertTTarget(CultureInfo, TTarget)	Overloaded. Tries to convert an Object specified in the obj parameter to the desired TTarget. See the Examples section of the ConvertTTarget(Object, CultureInfo) method for a related example. (Defined by ObjectExtensions.)

An object derived from UndoableObjectBase continuously tracks the property changes of properties, which are set through the IPersistableObject implementation and the ObservableObjectBase.Set method.

Note
When it is needed to be determined whether a type has undo/redo capability use the ICanUndo or ICanUndoRedo interfaces instead the UndoableObjectBase type because other undoable types, such as the ModelBase class are not necessarily derived from the UndoableObjectBase class. See also the class diagram of the business object base classes of the KGySoft.CoreLibraries assembly:

Differences from EditableObjectBase:
Both UndoableObjectBase and EditableObjectBase can revert changes; however, the aspects of these classes are different.

• An undoable class (which implements ICanUndo or ICanUndoRedo interfaces such as UndoableObjectBase) is able to undo (or redo) any changes made so far either step-by-step or in a single step.
• On the other hand, an editable class (which implements ICanEdit such as EditableObjectBase) is able to start editing sessions by saving a snapshot of its current state, which states are committable and revertible.
• Undo and editing features are independent from each other and a class is allowed to implement both (like the ModelBase class).

IRevertibleChangeTracking support:
UndoableObjectBase implements also the System.ComponentModel.IRevertibleChangeTracking interface, which is the standard way in .NET to support undoing.
This is how the IRevertibleChangeTracking members are mapped in the UndoableObjectBase class:

• IChangeTracking.IsChanged: Returns CanUndo.
• IChangeTracking.AcceptChanges: Calls ClearUndoHistory.
• IRevertibleChangeTracking.RejectChanges: Calls UndoAll.

IsModified vs. CanUndo:

• The IsModified property reflects the object's "dirty" state, meaning, it has been changed since the initialization or last save. The modified state can be cleared by the SetModified method. Clearing the modified state (eg. on saving the object) does not affect the undo capabilities, though.
• The CanUndo property tells whether there are any steps to undo. On saving an object the modified state can be cleared and still there can be undoable steps. And vice versa, undoing all steps will not clear the modified state.

Notes to Implementers
For an example see the Remarks section of the ObservableObjectBase class. The same applies also for the UndoableObjectBase class in terms of implementation.

Reference