C#的Command模式如何实现UI交互？

Execute(object parameter)

CanExecute(object parameter)

// 1. ICommand 接口（或者直接使用 System.Windows.Input.ICommand） public interface IMyCommand {     void Execute();     bool CanExecute();     event EventHandler CanExecuteChanged; // 用于通知UI更新CanExecute状态 }  // 2. Receiver 接收者 public class DocumentEditor {     public void Save(string content)     {         Console.WriteLine($"Saving document with content: '{content}'");         // 实际的保存逻辑，比如写入文件     }      public void Open(string path)     {         Console.WriteLine($"Opening document from path: '{path}'");         // 实际的打开逻辑     }      public bool IsDocumentOpen { get; private set; } = false; // 示例状态     public void SetDocumentOpen(bool isOpen)     {         IsDocumentOpen = isOpen;         OnDocumentStateChanged(); // 触发事件，通知相关命令更新CanExecute状态     }      public event EventHandler DocumentStateChanged;     protected virtual void OnDocumentStateChanged()     {         DocumentStateChanged?.Invoke(this, EventArgs.Empty);     } }  // 3. ConcreteCommand 具体命令：保存文档 public class SaveDocumentCommand : IMyCommand {     private readonly DocumentEditor _editor;     private readonly string _currentContent;      public SaveDocumentCommand(DocumentEditor editor, string content)     {         _editor = editor;         _currentContent = content;         // 订阅接收者的状态变化，以便更新CanExecute         _editor.DocumentStateChanged += (s, e) => OnCanExecuteChanged();     }      public event EventHandler CanExecuteChanged;      public void Execute()     {         _editor.Save(_currentContent);     }      public bool CanExecute()     {         // 只有当文档是打开状态时，才能保存         return _editor.IsDocumentOpen && !string.IsNullOrEmpty(_currentContent);     }      protected virtual void OnCanExecuteChanged()     {         CanExecuteChanged?.Invoke(this, EventArgs.Empty);     } }  // 4. 客户端（例如在WinForms的Form类中或WPF的ViewModel中） public class MyApplication {     private DocumentEditor _editor = new DocumentEditor();     private IMyCommand _saveCommand;      public MyApplication()     {         _saveCommand = new SaveDocumentCommand(_editor, "Hello World!");          // 假设这是一个按钮的点击事件处理         // buttonSave.Click += (sender, e) => _saveCommand.Execute();          // 模拟UI绑定，手动检查CanExecute并执行         SimulateUIInteraction();     }      private void SimulateUIInteraction()     {         Console.WriteLine("Initial state: Can Save? " + _saveCommand.CanExecute()); // Should be false          _editor.SetDocumentOpen(true); // 模拟文档打开         Console.WriteLine("After opening document: Can Save? " + _saveCommand.CanExecute()); // Should be true          if (_saveCommand.CanExecute())         {             _saveCommand.Execute(); // 模拟点击保存按钮         }          _editor.SetDocumentOpen(false); // 模拟文档关闭         Console.WriteLine("After closing document: Can Save? " + _saveCommand.CanExecute()); // Should be false     } }

button.Command = _saveCommand;

// 扩展后的可撤销命令接口 public interface IUndoableCommand : IMyCommand {     void Unexecute(); }  // 示例：一个可撤销的文本插入命令 public class InsertTextCommand : IUndoableCommand {     private DocumentEditor _editor;     private string _textToInsert;     private int _position; // 记录插入位置，以便撤销      public InsertTextCommand(DocumentEditor editor, string text, int position)     {         _editor = editor;         _textToInsert = text;         _position = position;         _editor.DocumentStateChanged += (s, e) => OnCanExecuteChanged();     }      public event EventHandler CanExecuteChanged;      public void Execute()     {         // 模拟在特定位置插入文本         Console.WriteLine($"Executing: Insert '{_textToInsert}' at position {_position}");         // _editor.InsertText(_textToInsert, _position); // 实际的文本操作     }      public void Unexecute()     {         // 模拟从特定位置删除文本         Console.WriteLine($"Unexecuting: Remove '{_textToInsert}' from position {_position}");         // _editor.DeleteText(_position, _textToInsert.Length); // 实际的文本操作     }      public bool CanExecute()     {         return _editor.IsDocumentOpen;     }      protected virtual void OnCanExecuteChanged()     {         CanExecuteChanged?.Invoke(this, EventArgs.Empty);     } }  // 命令管理器，负责维护历史 public class CommandManager {     private Stack<IUndoableCommand> _undoStack = new Stack<IUndoableCommand>();     private Stack<IUndoableCommand> _redoStack = new Stack<IUndoableCommand>();      public void ExecuteCommand(IUndoableCommand command)     {         if (command.CanExecute())         {             command.Execute();             _undoStack.Push(command);             _redoStack.Clear(); // 新操作清空重做历史             Console.WriteLine($"Command executed. Undo stack size: {_undoStack.Count}");         }     }      public void Undo()     {         if (_undoStack.Count > 0)         {             IUndoableCommand command = _undoStack.Pop();             command.Unexecute();             _redoStack.Push(command);             Console.WriteLine($"Undo executed. Undo stack size: {_undoStack.Count}, Redo stack size: {_redoStack.Count}");         }         else         {             Console.WriteLine("Nothing to undo.");         }     }      public void Redo()     {         if (_redoStack.Count > 0)         {             IUndoableCommand command = _redoStack.Pop();             command.Execute();             _undoStack.Push(command);             Console.WriteLine($"Redo executed. Undo stack size: {_undoStack.Count}, Redo stack size: {_redoStack.Count}");         }         else         {             Console.WriteLine("Nothing to redo.");         }     } }

Button

MenuItem