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));
}

-- 使用上特性[CallerMemberName]的作用就是由原本调用这个方法的使用要传入属性的名称作为这个方法的参数，但是现在就不用了，直接调用方法，会自动将参数（这里是属性的名称）传过去。所以调用就直接OnPropertyChanged()就行了，不需要原理的nameof(属性名)

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; }}
}