KGy SOFT

UndoableObjectBase Class

KGy SOFT Core Libraries Help
Represents an object with step-by-step undo/redo capabilities by adding ICanUndoRedo implementation to the PersistableObjectBase class. Undoing and redoing works for properties set through the IPersistableObject implementation and the ObservableObjectBase.Set method.
See the Remarks section for details.
Inheritance Hierarchy

SystemObject
  KGySoft.ComponentModelObservableObjectBase
    KGySoft.ComponentModelPersistableObjectBase
      KGySoft.ComponentModelUndoableObjectBase

Namespace:  KGySoft.ComponentModel
Assembly:  KGySoft.CoreLibraries (in KGySoft.CoreLibraries.dll) Version: 5.0.0-rc.1
Syntax

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

The UndoableObjectBase type exposes the following members.

Constructors

  NameDescription
Protected methodUndoableObjectBase
Initializes a new instance of the UndoableObjectBase class
Top
Properties

  NameDescription
Public propertyCanRedo
Gets whether there are changes to redo.
Public propertyCanUndo
Gets whether there are changes to undo.
Public propertyIsModified
Gets whether this instance has been modified. Modified state can be set by the SetModified method.
(Inherited from ObservableObjectBase.)
Protected propertyUndoCapacity
Gets or sets the undo capacity.
Default value: 20.
Top
Methods

  NameDescription
Protected methodAffectsModifiedState
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).)
Protected methodCanGetProperty
Gets whether the specified property can be get.
The base implementation allows to get the actual instance properties in this instance.
(Inherited from ObservableObjectBase.)
Protected methodCanSetProperty
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.)
Public methodClearUndoHistory
Clears the undo/redo history without performing any undo.
Public methodClone
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.)
Public methodDispose
Releases the resources held by this instance.
(Inherited from ObservableObjectBase.)
Protected methodDispose(Boolean)
Releases the resources held by this instance.
The base implementation removes the subscribers of the PropertyChanged event.
(Inherited from ObservableObjectBase.)
Public methodEquals
Determines whether the specified object is equal to the current object.
(Inherited from Object.)
Protected methodFinalize
Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.
(Inherited from Object.)
Protected methodGetT(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.)
Protected methodGetT(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.)
Public methodGetHashCode
Serves as the default hash function.
(Inherited from Object.)
Public methodGetType
Gets the Type of the current instance.
(Inherited from Object.)
Protected methodMemberwiseClone
Creates a shallow copy of the current Object.
(Inherited from Object.)
Protected methodOnPropertyChanged
Raises the PropertyChanged event.
(Overrides ObservableObjectBaseOnPropertyChanged(PropertyChangedExtendedEventArgs).)
Public methodRedoAll
Redoes all possible redo steps.
Protected methodResetProperty
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.)
Protected methodResumeChangedEvent
Resumes the raising of the PropertyChanged event suspended by the SuspendChangeEvents method.
(Inherited from ObservableObjectBase.)
Protected methodSet
Sets the value of a property.
For an example, see the Remarks section of the ObservableObjectBase class.
(Inherited from ObservableObjectBase.)
Public methodSetModified
Sets the modified state of this ObservableObjectBase instance represented by the IsModified property.
(Inherited from ObservableObjectBase.)
Protected methodSuspendChangedEvent
Suspends the raising of the PropertyChanged event until ResumeChangeEvents method is called. Supports nested calls.
(Inherited from ObservableObjectBase.)
Public methodToString
Returns a string that represents the current object.
(Inherited from Object.)
Public methodTryRedo
Tries to perform one redo step.
Public methodTryUndo
Tries to perform one undo step.
Public methodUndoAll
Undoes all possible undo steps.
Top
Events

  NameDescription
Public eventPropertyChanged
Occurs when a property value changed. The actual type of the event argument is PropertyChangedExtendedEventArgs.
(Inherited from ObservableObjectBase.)
Top
Extension Methods

  NameDescription
Public Extension MethodConvert(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.)
Public Extension MethodCode exampleConvertTTarget(CultureInfo)Overloaded.
Converts an Object specified in the obj parameter to the desired TTarget.
(Defined by ObjectExtensions.)
Public Extension MethodIn (Defined by ObjectExtensions.)
Public Extension MethodTryConvert(Type, Object)Overloaded.
Tries to convert an Object specified in the obj parameter to the desired targetType.
(Defined by ObjectExtensions.)
Public Extension MethodTryConvert(Type, CultureInfo, Object)Overloaded.
Tries to convert an Object specified in the obj parameter to the desired targetType.
(Defined by ObjectExtensions.)
Public Extension MethodTryConvertTTarget(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.)
Public Extension MethodTryConvertTTarget(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.)
Top
Remarks

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 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:
Class diagram of business object base classes

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:

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.

Note 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.
See Also

Reference