为什么不同的实例具有相同的依赖属性值?

时间:2014-01-06 09:24:18

标签: c# wpf dependency-properties

当我尝试在WPF / .NET 3.5中开发自定义控件时出现严重问题。

详细

1.当我在同一个窗口中添加两个实例时,看起来第二个将始终具有第一个的依赖属性值,即使test2只是在不应用模板的情况下构造(例如:tes2.TopItems / CenterItems / BottomItems与tes1相同,包括Count,Items ...)。

2.当我删除其中任何一个时,它会好的。

3. TopItems / CenterItems / BottomItems在OnApplyTemplate()中初始化。

4.更改属性“Calendar”和“CalendarViewType”将调用PropertyChangedCallBack()。

5.“TopItems”,“CenterItems”,“BttomItems”用于控件模板中的{TemplateBinding}。

6.我尝试使用“Normal Property”“{Binding RelativeSource = TemplatedParent}”而不是“Depdendency Property”和{TemplateBinding},它运作良好! !!!多么奇怪!!!

请问,任何人都可以提供帮助吗?感谢looooooooooooooot!

类窗口

<Window>
 <Grid>
  <common:CalendarTitle x:Name="test1" Calendar="{Binding Calendar}" CalendarViewType="Month_Week"></common:CalendarTitle>
  <common:CalendarTitle x:Name="test2" Calendar="{Binding Calendar}"></common:CalendarTitle>
 </Grid>
</Window>

类CalendarTile:Control

    public static readonly DependencyProperty CalendarProperty = DependencyProperty.Register("Calendar", typeof(ICalendar), typeof(CalendarTitle), new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.AffectsRender, PropertyChangedCallback));
    public static readonly DependencyProperty CalendarViewTypeProperty = DependencyProperty.Register("CalendarViewType", typeof(CalendarViewType), typeof(CalendarTitle), new FrameworkPropertyMetadata(CalendarViewType.Week_Day, FrameworkPropertyMetadataOptions.AffectsRender, PropertyChangedCallback));
    public static readonly DependencyProperty TopItemsProperty = DependencyProperty.Register("TopItems", typeof(IEnumerable<ICalendarItem>), typeof(CalendarTitle), new FrameworkPropertyMetadata(new ObservableCollection<ICalendarItem>()));
    public static readonly DependencyProperty CenterItemsProperty = DependencyProperty.Register("CenterItems", typeof(IEnumerable<ICalendarItem>), typeof(CalendarTitle), new FrameworkPropertyMetadata(new ObservableCollection<ICalendarItem>()));
    public static readonly DependencyProperty BottomItemsProperty = DependencyProperty.Register("BottomItems", typeof(IEnumerable<ICalendarItem>), typeof(CalendarTitle), new FrameworkPropertyMetadata(new ObservableCollection<ICalendarItem>()));
    public IEnumerable<ICalendarItem> TopItems
    {
        get { return (IEnumerable<ICalendarItem>)GetValue(TopItemsProperty); }
        set { SetValue(TopItemsProperty, value); }
    }
    public IEnumerable<ICalendarItem> CenterItems
    {
        get { return (IEnumerable<ICalendarItem>)GetValue(CenterItemsProperty); }
        set { SetValue(CenterItemsProperty, value); }
    }
    public IEnumerable<ICalendarItem> BottomItems
    {
        get { return (IEnumerable<ICalendarItem>)GetValue(BottomItemsProperty); }
        set { SetValue(BottomItemsProperty, value); }
    }

PropertyCallBack()

 static void PropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var calendarTile = (CalendarTitle)d;
        calendarTile.isLoaded = false;
        calendarTile.OnApplyTemplate();
    }

OnApplyTemplate()

 public override void OnApplyTemplate()
    {
        if (!isLoaded)
        {
            ClearItems();
            if (Calendar != null)
                PopulateItems();
            isLoaded = true;
        }
    }

PopulateItems()

 private void PopulateItems()
    {
        switch (CalendarViewType)
        {
            case CalendarViewType.Week_Day:
                {
                    foreach (var item in Calendar.Items)
                    {
                        if (item.Date.DayOfWeek == DayOfWeek.Sunday)
                            (TopItems as IList<ICalendarItem>).Add(item);
                    }
                    CenterItems = BottomItems = Calendar.Items;
                    break;
                }

            case CalendarViewType.Month_Week:
                {
                    foreach (var item in Calendar.Items)
                    {
                        if (item.Date.DayOfYear == 1)
                            (TopItems as IList<ICalendarItem>).Add(item);
                        if (item.Date.Day == 1)
                            (CenterItems as IList<ICalendarItem>).Add(item);
                        if (item.Date.DayOfWeek == DayOfWeek.Monday)
                            (BottomItems as IList<ICalendarItem>).Add(item);
                    }
                    break;
                }

            case CalendarViewType.Year_Month:
                {
                    foreach (var item in Calendar.Items)
                    {
                        if (item.Date.DayOfYear == 1)
                            (TopItems as IList<ICalendarItem>).Add(item);
                        if (item.Date.Day == 1)
                            (CenterItems as IList<ICalendarItem>).Add(item);
                        if (item.Date.DayOfWeek == DayOfWeek.Monday)
                            (BottomItems as IList<ICalendarItem>).Add(item);
                    }
                    break;
                }
        }

    }

1 个答案:

答案 0 :(得分:11)

指定依赖项属性的默认值时,将在所有实例之间共享此默认值。因此,如果它是一个可变的引用类型,就像一个集合,对该集合的任何更改都将反映在该类的所有实例中。

您应该将默认值保留为null,并在类构造函数中初始化集合。这样,该类的所有实例都将拥有自己的集合。