我没有运气试图将数据集合绑定到我的自定义控件的属性。我已经实现了该控件的字符串属性的机制(这里有一点帮助),并期望集合类型一样简单。但是,我无法使其再次工作。
这是我的自定义控件视图
<UserControl x:Class="BadaniaOperacyjne.Controls.Matrix"
mc:Ignorable="d" Name="CustomMatrix"
d:DesignHeight="300" d:DesignWidth="300">
<Grid>
<Grid.RowDefinitions>
<!-- ... -->
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<!-- ... -->
</Grid.ColumnDefinitions>
<TextBlock Grid.Row="0" Grid.Column="1" Text="{Binding ElementName=CustomMatrix, Path=Title}"/>
<Grid Grid.Row="2" Grid.Column="1" Name="contentGrid">
<ListBox ItemsSource="{Binding ElementName=CustomMatrix, Path=ItemsList}">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
</Grid>
</UserControl>
及其代码背后
#region ItemsList Property
public static readonly DependencyProperty ItemsListProperty =
DependencyProperty.Register("ItemsList", typeof(ObservableCollection<object>), typeof(Matrix), new PropertyMetadata(new ObservableCollection<object>(), new PropertyChangedCallback(ItemsListChanged)));
public ObservableCollection<object> ItemsList
{
get { return GetValue(ItemsListProperty) as ObservableCollection<object>; }
set { SetValue(ItemsListProperty, value); }
}
private void ItemsListChanged(object value)
{
System.Diagnostics.Debug.WriteLine("matrix: items list changed " + value);
if (ItemsList != null)
{
ItemsList.CollectionChanged += ItemsList_CollectionChanged;
System.Diagnostics.Debug.WriteLine("got " + string.Join(",", ItemsList.ToList()));
}
else
{
System.Diagnostics.Debug.WriteLine("got null");
}
}
void ItemsList_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
System.Diagnostics.Debug.WriteLine("matrix: current items list collection changed");
}
private static void ItemsListChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
// a breakpoint
((Matrix)d).ItemsListChanged(e.NewValue);
}
#endregion
// showing the Title property implementation just to state that
// it is done the same way as for ItemsList
#region Title Property
public static readonly DependencyProperty TitleProperty =
DependencyProperty.Register("Title", typeof(string), typeof(Matrix), new PropertyMetadata("", new PropertyChangedCallback(TitleChanged)));
public string Title
{
get { return (string)GetValue(TitleProperty); }
set { SetValue(TitleProperty, value); }
}
private void TitleChanged(string title)
{
System.Diagnostics.Debug.WriteLine("matrix: title changed to: " + title);
}
private static void TitleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
((Matrix)d).TitleChanged((string)e.NewValue);
}
#endregion
这就是我试图绑定到该控件的方式
<custom:Matrix x:Name="customMatrix" DockPanel.Dock="Top" Title="{Binding Title}" ItemsList="{Binding Items}"/>
而主页的代码是
//internal ObservableCollection<List<int>> ItemsList { get; set; }
public class ViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public ViewModel()
{
Items = new ObservableCollection<int> { 1, 2, 3, 4, 5, 6};
}
void Items_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
System.Diagnostics.Debug.WriteLine("problem manager: items list changed " + e.NewItems.Count);
}
public ObservableCollection<int> Items { get; set; }
protected string title;
public string Title
{
get { return title; }
set
{
if (title != value)
{
title = value;
NotifyPropertyChanged("Title");
}
}
}
protected void NotifyPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
public ViewModel VM { get; private set; }
// this is the window constructor
private ProblemManager()
{
VM = new ViewModel();
DataContext = VM;
InitializeComponent();
VM.Title = "title";
}
private int i = 0;
private void btnAddRow_Click(object sender, RoutedEventArgs e)
{
// when doing either of these two lines below,
// the control breakpoint is never hit
VM.Items.Add(++i);
VM.Items = new ObservableCollection<int> { 2, 3 };
// however, when directly assigning to the control's property,
// the event is raised and the breakpoint is hit and the UI is updated
customMatrix.ItemsList = new ObservableCollection<object> { 1, 2, 3 };
customMatrix.ItemsList.Add(66);
// and this of course makes the control's title update
VM.Title = (++i).ToString();
}
我相信,两者都是DependencyProperty
针对控件的,Title
并且ItemsList
创建方式相同。尽管如此,绑定可能无法正常工作,因为该ItemsListChanged
绑定未引发事件。因此,问题在于我无法ViewModel.Items
通过XAML将窗口的集合绑定到控件的ItemsList
集合。DependencyProperty
在控件中为集合创建值与DependencyProperty
为简单string
属性创建值有区别吗?
问题出在您的DependencyProperty
注册中。Co-variance is not applicable for generic lists
也就是说,你不能这样做-
ObservableCollection<object> objects = new ObservableCollection<int>();
您已将DP的类型声明为,ObservableCollection<object>
但将其与type列表绑定ObservableCollection<int>
。
您应该change either type of DP to ObservableCollection<int>
OR change binding collection type to ObservableCollection<object>
。
public ViewModel()
{
Items = new ObservableCollection<object> { 1, 2, 3, 4, 5, 6};
}
public ObservableCollection<object> Items { get; set; }
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