[C#][转载]实现richtextbox的多步撤消（Undo、Redo）？

下面是针对textbox的。高手参照此资料做一个richtextbox, [C#]可以进行多步撤消（Undo、Redo）的TextBox  默认的TextBox只能进行一步撤消，且不存在Redo操作（二次撤消相当于一次Redo）。以下这个组件实现了TextBox的多步撤消（Undo、Redo）操作，代码改编于Kevin.SyntaxTextBox（原代码是针对RichTextBox实现的Undo、Redo功能）。  using System;  using System.Collections.Generic;  using System.Windows.Forms;  namespace Ekinglong.Drawing.Forms   {       /// <summary>      /// 可以执行多步撤消操作的TextBox      /// </summary>      public partial class TextBoxEx : TextBox       {          //Undo/Redo members          private List<UndoRedoInfo> mUndoList = new List<UndoRedoInfo>();          private Stack<UndoRedoInfo> mRedoStack = new Stack<UndoRedoInfo>();          private bool mIsUndo = false;          private UndoRedoInfo mLastInfo = new UndoRedoInfo("", 0);          private int mMaxUndoRedoSteps = 50;           /// <summary>          /// The on text changed overrided.          /// </summary>          /// <param name="e"></param>          protected override void OnTextChanged(EventArgs e)           {              base.OnTextChanged(e);              if (!mIsUndo)               {                  mRedoStack.Clear();                  mUndoList.Insert(0, mLastInfo);                  this.LimitUndo();                  mLastInfo = new UndoRedoInfo(Text, SelectionStart);              }              //Invalidate();          }           /// <summary>          /// 设置和获取撤消操作允许的最大步数          /// </summary>          public int MaxUndoRedoSteps           {               set { mMaxUndoRedoSteps = value; }               get { return mMaxUndoRedoSteps; }          }           /// <summary>          /// 清空Undo、Redo操作信息          /// </summary>          public void ClearUndoAndRedo()           {              mUndoList.Clear();              mRedoStack.Clear();          }           /// <summary>          /// 判断是否可以进行Undo操作          /// </summary>          public new bool CanUndo           {               get { return mUndoList.Count > 0; }          }           /// <summary>          /// 判断是否可以进行Redo操作          /// </summary>          public bool CanRedo           {               get { return mRedoStack.Count > 0; }          }           /// <summary>          /// 撤消操作          /// </summary>          public new void Undo()           {              if (!CanUndo)                  return;              mIsUndo = true;              mRedoStack.Push(new UndoRedoInfo(Text, SelectionStart));              UndoRedoInfo info = (UndoRedoInfo)mUndoList[0];              mUndoList.RemoveAt(0);              Text = info.Text;              SelectionStart = info.CursorLocation;              ScrollToCaret();              mLastInfo = info;              mIsUndo = false;          }           /// <summary>          /// 重复操作          /// </summary>          public void Redo()           {              if (!CanRedo)                  return;              mIsUndo = true;              mUndoList.Insert(0, new UndoRedoInfo(Text, SelectionStart));              LimitUndo();              UndoRedoInfo info = (UndoRedoInfo)mRedoStack.Pop();              Text = info.Text;              SelectionStart = info.CursorLocation;              ScrollToCaret();              mIsUndo = false;          }          private void LimitUndo()           {              while (mUndoList.Count > mMaxUndoRedoSteps)               {                  mUndoList.RemoveAt(mMaxUndoRedoSteps);              }          }          private class UndoRedoInfo           {              public UndoRedoInfo(string text, int cursorLoc)               {                  Text = text;                  CursorLocation = cursorLoc;              }              public readonly int CursorLocation;              public readonly string Text;          }      }  }