Question

现在我有一个只显示一个月的日历（我传递的月份）。我试图让用户从comboBox中选择月份和年份并更新日历。我使用observablecollection绑定，我很熟悉。我不知道INotifyPropertyChanged如何工作。我以前从未使用过它。非常感谢任何帮助或建议。这就是我到目前为止所做的：

public class Schedule : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    public void Update(int propertyName)
    {
        if (propertyName != null)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
                 handler.Invoke(this, new PropertyChangedEventArgs(propertyName.ToString()));
        }
    }


   // public void UpdateCal(PropertyChangedEventArgs e)
   // {
    //    if (PropertyChanged != null)
    //        PropertyChanged(this, e);
  //  } 
    public string MonthWeek { get; set; }
    public string Year { get; set; }
    public string Month { get; set; }
    public string day { get; set; }
    public string WeekOfYear { get; set; }
    public string dayofweek { get; set; }

   // public string month {
    //    get {return Month; }
    //    set
    //    {
     //       UpdateCal(new PropertyChangedEventArgs("month"));
      //  }
   // }
    public int WeekNo { get; set; }
    public int WeekDay { get; set; }
    public DateTime Date { get; set; }
 }

---这是另一个确定每个日期在网格上的位置的类----

           public SchedulePage(MainWindow parentForm)
    {
        InitializeComponent();

        pick = Convert.ToInt32(comboMonth.SelectedItem) + 1;
        _parentForm = parentForm;
        // DateTime date = new DateTime(year, month, day);
        var t = new List<Schedule>();
        DateTime curr = DateTime.Now;
      //  comboMonth.Items.Add(curr.Month);
        DateTime newcurr = new DateTime(2011, pick, 1);
     //   pickdate = datePickercal.SelectedDate;
      //  DateTime newcurr = new DateTime(curr.Year, curr.Month, 1);
        var cal = System.Globalization.DateTimeFormatInfo.CurrentInfo.Calendar;
        var ms = cal.GetWeekOfYear(new DateTime(newcurr.Year, newcurr.Month, 1), System.Globalization.CalendarWeekRule.FirstDay, System.DayOfWeek.Sunday);
        for (var i = 1; newcurr.Month == pick; newcurr = newcurr.AddDays(1))
        {
            var sched = new Schedule();
            var month_week = (newcurr.Day / 7) ;
            sched.MonthWeek = newcurr.GetWeekOfMonth().ToString();
            sched.Month = newcurr.Month.ToString();
            sched.Year = newcurr.Year.ToString();
            sched.day = newcurr.Day.ToString();
            sched.WeekOfYear = cal.GetWeekOfYear(newcurr, System.Globalization.CalendarWeekRule.FirstDay, DayOfWeek.Sunday).ToString();
            sched.dayofweek = newcurr.DayOfWeek.ToString();
            t.Add(sched);

                _parentForm.bindings.schedule.Add(new Schedule { WeekNo = newcurr.GetWeekOfMonth()-1, WeekDay = (int)newcurr.DayOfWeek, day = newcurr.Day.ToString() });

        }
        lblDate.Content = (newcurr.Month -1) + "/" + newcurr.Year;

         DataContext = _parentForm.Bindings;

---这个类使得observablecollections -----

           public partial class BindingCamper 
{  // This class assist in binding campers from listview to the textboxes on the camperspage
    public ObservableCollection<Camper> Campers { get; set; }
    public ObservableCollection<Staff> StaffMembers { get; set; }
    public ObservableCollection<Schedule> schedule { get; set; }
    public BindingCamper()
    {
        Campers = new ObservableCollection<Camper>();
      StaffMembers = new ObservableCollection<Staff>();
      schedule = new ObservableCollection<Schedule>();
    }

Answer 1

这是您通常实施INotifyPropertyChanged的方式：

public class Schedule : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        var handler = PropertyChanged;
        if (handler != null)
            handler(this, new PropertyChangedEventArgs(propertyName));
    }

    private string _monthWeek;
    public string MonthWeek
    {
        get { return _monthWeek; }
        set
        {
            if (value != _monthWeek)
            {
                _monthWeek = value;
                OnPropertyChanged("MonthWeek");
            }
        }
    }

    // And so on for other properties...

}

基本上，每次更新属性时都需要触发PropertyChanged事件，因此每个setter都必须调用OnPropertyChanged。请注意，您无法使用自动实现的属性执行此操作，因为您需要在setter中添加自定义逻辑。

Answer 2

绑定到属性时（即使该属性是ObservableCollection），对PROPERTY的任何更改（不是属性的内容）都应该引发PropertyChanged事件。

当提升CollectionChanged事件时，ObservableCollection是自包含的，所以不要担心会触发ItemsSource项本身的事件。

XAML：

<!-- This says that ItemsSource is bound to the Campers property... -->
<ItemsControl ItemsSource="{Binding Path=Campers, Mode=OneWay}" />

CLASS：

public class TheViewModel()
{
   private ObservableCollection<Camper> _campers;
   public ObservableCollection<Camper> Campers
   {
       get { return _campers; }
       set
       {
           if (Equals(_campers, value)) return;

           _campers = value;
           RaisePropertyChanged("Campers"); //Or however you implement it
       }
   }

   private void SomeFunc()
   {
       var bindingCamper = new BindingCamper();

       Campers = bindingCamper.Campers; //This will fire the event
       //etc.
   }

}

或者，如果你是BindingCamper 你的ViewModel那么你在那里做同样的事情。

Answer 3

当您从代码后面更改属性并且想要更新UI时，则使用INotifyPropertyChanged接口。正如我所看到你实现了接口甚至设置了一个帮助器来使用它只是你使用了一个int作为参数，你应该使用一个字符串。如果你设置了属性，那么只需使用正确的PropertyName调用你的帮助器，你就可以了。

像这样：

 public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(String propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (null != handler)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }

并触发事件通知用户界面：

NotifyPropertyChanged("YourPropertyName");

也许你需要设置TwoWay绑定，但只有你想从UI更改属性时才会这样。

INotifyPropertyChanged和ObservableCollection WPF

3 个答案: