←Select platform

BeginUndo Method

Summary

Creates a new undo node in this AnnAutomation object.

Syntax

C++

public virtual void BeginUndo()

Public Overridable Sub BeginUndo()

public: 
virtual void BeginUndo();

Remarks

Use this method along with the EndUndo and CancelUndo methods to programmatically add a node to the undo stack maintained by this AnnAutomation. Typically, you add an undo node as follows:

Call the BeginUndo method before you make any changes to create a new node.
Perform any changes to the AnnAutomation object.
Call the EndUndo method to commit this undo node into the undo stack of the AnnAutomation object.
In case of errors (typically in a catch statement), call the CancelUndo method to remove the node and cancel the operation.

You do not need to manually call the BeginUndo, EndUndo or CancelUndo methods when calling methods from this AnnAutomation object directly. The AnnAutomation object will internally do this for you. For example, when you call the Delete method to delete the object(s) currently being edited, the AnnAutomation object will perform the above sequence internally to add the undo node.

Use the UndoCapacity property to get or set the number of user actions that can be reversed using the Undo method, or re-applied using the Redo method. The default for the UndoCapacity property is 10 actions.

For more information, refer to Undoing WPF Automation Operations.

Example

This example will manually add a new rectangle object to an automation object and then start editing it.

Silverlight C#

Silverlight VB

Imports Leadtools.Windows.Controls 
Imports Leadtools.Windows.Annotations 
 
Private Sub AnnAutomation_BeginUndo(ByVal automation As AnnAutomation) 
   ' first create a new undo node 
   automation.BeginUndo() 
   Try 
      ' add a new rectangle object 
      Dim rectObj As AnnRectangleObject = New AnnRectangleObject() 
      rectObj.Rect = New Rect(100, 100, 200, 200) 
 
      rectObj.Stroke = Colors.Blue 
      rectObj.StrokeThickness = 2.0 
      rectObj.Fill = Colors.Yellow 
 
      automation.Container.Children.Add(rectObj) 
 
      ' "select" this object 
      automation.StartEditing(rectObj, False) 
 
      ' commit the undo node 
      automation.EndUndo() 
   Catch ex As Exception 
      ' in case of errors, cancel the undo node 
      automation.CancelUndo() 
      Throw ex 
   End Try 
 
   MessageBox.Show("Object has been added as is now selected.  Next will call //Undo// to undo the operation") 
   automation.Undo() 
   MessageBox.Show("Operation has been undone.  Next will call //Redo// to redo the operation") 
   automation.Redo() 
   MessageBox.Show("Object should be back and selected") 
End Sub

using Leadtools.Windows.Controls; 
using Leadtools.Windows.Annotations; 
using Leadtools.Demos; 
using Leadtools.Help; 
 
private void AnnAutomation_BeginUndo(AnnAutomation automation) 
{ 
   // first create a new undo node 
   automation.BeginUndo(); 
   try 
   { 
      // add a new rectangle object 
      AnnRectangleObject rectObj = new AnnRectangleObject(); 
      rectObj.Rect = new Rect(100, 100, 200, 200); 
      rectObj.Stroke = Colors.Blue; 
      rectObj.Fill = Colors.Yellow; 
 
      rectObj.StrokeThickness = 2.0; 
 
      automation.Container.Children.Add(rectObj); 
 
      // "select" this object 
      automation.StartEditing(rectObj, false); 
 
      // commit the undo node 
      automation.EndUndo(); 
   } 
   catch(Exception ex) 
   { 
      // in case of errors, cancel the undo node 
      automation.CancelUndo(); 
      throw ex; 
   } 
 
   MessageBox.Show("Object has been added as is now selected.  Next will call //Undo// to undo the operation"); 
   automation.Undo(); 
   MessageBox.Show("Operation has been undone.  Next will call //Redo// to redo the operation"); 
   automation.Redo(); 
   MessageBox.Show("Object should be back and selected"); 
}

using Leadtools.Windows.Controls; 
using Leadtools.Windows.Annotations; 
using Leadtools.Examples; 
using Leadtools.Silverlight.Demos; 
 
private void AnnAutomation_BeginUndo(AnnAutomation automation) 
{ 
   // first create a new undo node 
   automation.BeginUndo(); 
   try 
   { 
      // add a new rectangle object 
      AnnRectangleObject rectObj = new AnnRectangleObject(); 
      rectObj.Rect = new Rect(100, 100, 200, 200); 
      rectObj.Stroke = Colors.Blue; 
      rectObj.Fill = Colors.Yellow; 
 
      rectObj.StrokeThickness = 2.0; 
 
      automation.Container.Children.Add(rectObj); 
 
      // "select" this object 
      automation.StartEditing(rectObj, false); 
 
      // commit the undo node 
      automation.EndUndo(); 
   } 
   catch(Exception ex) 
   { 
      // in case of errors, cancel the undo node 
      automation.CancelUndo(); 
      throw ex; 
   } 
 
   MessageBox.Show("Object has been added as is now selected.  Next will call //Undo// to undo the operation"); 
   automation.Undo(); 
   MessageBox.Show("Operation has been undone.  Next will call //Redo// to redo the operation"); 
   automation.Redo(); 
   MessageBox.Show("Object should be back and selected"); 
}

Imports Leadtools.Windows.Controls 
Imports Leadtools.Windows.Annotations 
Imports Leadtools.Silverlight.Demos 
 
Private Sub AnnAutomation_BeginUndo(ByVal automation As AnnAutomation) 
   ' first create a new undo node 
   automation.BeginUndo() 
   Try 
      ' add a new rectangle object 
      Dim rectObj As AnnRectangleObject = New AnnRectangleObject() 
      rectObj.Rect = New Rect(100, 100, 200, 200) 
      rectObj.Stroke = Colors.Blue 
      rectObj.Fill = Colors.Yellow 
 
      rectObj.StrokeThickness = 2.0 
 
      automation.Container.Children.Add(rectObj) 
 
      ' "select" this object 
      automation.StartEditing(rectObj, False) 
 
      ' commit the undo node 
      automation.EndUndo() 
   Catch ex As Exception 
      ' in case of errors, cancel the undo node 
      automation.CancelUndo() 
      Throw ex 
   End Try 
 
   MessageBox.Show("Object has been added as is now selected.  Next will call //Undo// to undo the operation") 
   automation.Undo() 
   MessageBox.Show("Operation has been undone.  Next will call //Redo// to redo the operation") 
   automation.Redo() 
   MessageBox.Show("Object should be back and selected") 
End Sub