今天我发现FW 4.5有自己的撤消/重做管理器（如果我理解正确的话）http://msdn.microsoft.com/en-us/library/System.ComponentModel.Design.UndoEngine%28v=vs.110%29.aspx
嗯，我找不到任何关于如何开始使用这个类来制作基于文本控件的简单撤消/重做的示例，我知道其他可用于执行撤消操作的方法，但是我只想学习如何使用这个功能。
当我尝试使用构造函数时，没有要传递的任何参数，而且Intellisense也没有显示给我System.ComponentModel.Design.UndoEngine类的任何方法，真的不知道该怎么用它。
有人能为我们提供C#或VBNET的示例吗？（如果可能的话，请提供VBNET文档）
UndoEngine是一个抽象类，Visual Studio和设计师在各自的方式中实现了UndoEngine，并且这些实现必须是私有的或不可重新分发的。你将无法使用它，实际上抽象类只是一个具有少量实现的接口，它根本不是一个撤销框架。
尽管如此，仍然需要编写自己的撤销管理，但是从UndoEngine类派生你的撤销引擎的好处是，它可以轻松地与VS和其他基于MS的编辑器集成。
最简单的UndoEngine实现：
假设你正在更改一个全局变量，
// following code uses big UndoUnit
public void SetGlobalVariable(object v){
var oldValue = GlobalVariable;
GlobalVariable = v;
var action = new UndoUnit{
UndoAction = ()=>{
GlobalVariable = oldValue;
},
RedoAction = ()=>{
GlobalVariable = v;
}
};
UndoManager.Add(action);
}
/// <summary>
/// Used to indicates the designer's status
/// </summary>
public enum UndoUnitState
{
Undoing,
Redoing,
}
/// <summary>
/// A UndoUnitBase can be used as a IOleUndoUnit or just a undo step in
/// a transaction
/// </summary>
public class UndoUnitBase : IOleUndoUnit
{
public Action UndoAction {get;set;}
public Action RedoAction {get;set;}
private string name = null;
private Guid clsid = Guid.Empty;
private bool inDoAction = false;
private bool isStillAtTop = true;
private UndoUnitState unitState = UndoUnitState.Undoing;
protected UndoUnit UnitState
{
get { return unitState; }
set { unitState = value; }
}
/// <summary>
/// </summary>
/// <param name="undoManager"></param>
/// <param name="name"></param>
internal UndoUnitBase(string name)
{
this.name = name;
}
~UndoUnitBase()
{
}
/// <summary>
/// </summary>
protected bool InDoAction
{
get
{
return inDoAction;
}
}
public string UndoName
{
get
{
return name;
}
set
{
this.name = value;
}
}
public Guid Clsid
{
get { return clsid; }
set { clsid = value; }
}
/// <summary>
/// This property indicates whether the undo unit is at the top (most recently added to)
/// the undo stack. This is useful to know when deciding whether undo units for operations
/// like typing can be coallesced together.
/// </summary>
public bool IsStillAtTop
{
get { return isStillAtTop; }
}
/// <summary>
/// This function do the actual undo, and then revert the action to be a redo
/// </summary>
/// <returns>objects that should be selected after DoAction</returns>
protected abstract void DoActionInternal();
/// <devdoc>
/// IOleUndoManager's "Do" action.
/// </devdoc>
void IOleUndoUnit.Do(IOleUndoManager oleUndoManager)
{
Do(oleUndoManager);
}
protected virtual int Do(IOleUndoManager oleUndoManager)
{
try
{
if(unitState== UndoUnitState.Undoing){
UndoAction();
}else{
RedoAction();
}
unitState = (unitState == UndoUnitState.Undoing) ? UndoUnitState.Redoing : UndoUnitState.Undoing;
if (oleUndoManager != null)
oleUndoManager.Add(this);
return VSConstants.S_OK;
}
catch (COMException e)
{
return e.ErrorCode;
}
catch
{
return VSConstants.E_ABORT;
}
finally
{
}
}
/// <summary>
/// </summary>
/// <returns></returns>
void IOleUndoUnit.GetDescription(out string pBstr)
{
pBstr = name;
}
/// <summary>
/// </summary>
/// <param name="clsid"></param>
/// <param name="pID"></param>
/// <returns></returns>
void IOleUndoUnit.GetUnitType(out Guid pClsid, out int plID)
{
pClsid = Clsid;
plID = 0;
}
/// <summary>
/// </summary>
void IOleUndoUnit.OnNextAdd()
{
// We are no longer the top most undo unit; another one was added.
isStillAtTop = false;
}
}
public class MyUndoEngine : UndoEngine, IUndoHandler
{
Stack<UndoEngine.UndoUnit> undoStack = new Stack<UndoEngine.UndoUnit>();
Stack<UndoEngine.UndoUnit> redoStack = new Stack<UndoEngine.UndoUnit>();
public ReportDesignerUndoEngine(IServiceProvider provider) : base(provider)
{
}
#region IUndoHandler
public bool EnableUndo {
get {
return undoStack.Count > 0;
}
}
public bool EnableRedo {
get {
return redoStack.Count > 0;
}
}
public void Undo()
{
if (undoStack.Count > 0) {
UndoEngine.UndoUnit unit = undoStack.Pop();
unit.Undo();
redoStack.Push(unit);
}
}
public void Redo()
{
if (redoStack.Count > 0) {
UndoEngine.UndoUnit unit = redoStack.Pop();
unit.Undo();
undoStack.Push(unit);
}
}
#endregion
protected override void AddUndoUnit(UndoEngine.UndoUnit unit)
{
undoStack.Push(unit);
}
}
AddUndoUnit，让人感觉它就像一个框架（即你仍然需要添加很多东西，如检测更改-这是困难的部分），而不是Etienne的方法。如果你认为Etienne的方法很复杂，请看看UndoUnit的文档：http://msdn.microsoft.com/en-us/library/system.componentmodel.design.undoengine.undounit(v=vs.110).aspx - Ňɏssa Pøngjǣrdenlarp