背景：PropertyChanged和Command总是没有记住怎么写

PropertyChanged：

public event PropertyChangedEventHandler? PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}

RelayCommand：

public class RelayCommand : ICommand
{private readonly Action<object> _execute;private readonly Predicate<object> _canExecute;public RelayCommand(Action<object> execute, Predicate<object> canExecute = null){_execute = execute ?? throw new ArgumentNullException(nameof(execute));_canExecute = canExecute;}public bool CanExecute(object parameter){return _canExecute == null || _canExecute(parameter);}public void Execute(object parameter){_execute(parameter);}public event EventHandler CanExecuteChanged{add { CommandManager.RequerySuggested += value; }remove { CommandManager.RequerySuggested -= value; }}
}