将集合绑定到自定义控件属性 [英] Binding a collection to a custom control property
问题描述
我没有运气试图绑定数据集合到我的自定义控件的属性。我已经实现了这个控件的字符串属性的机制(从这里一个小帮助),并希望集合类型是容易的。
I am having no luck trying to bind a collection of data to my custom control its property. I already have implemented the mechanism for a string property of this control (with a small help from here) and expected the collection type to be as easy. However I cannot make it work again.
Here is my custom control view
这是我的自定义控制视图
<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>
及其代码隐藏
#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
这里是我试图绑定到控制
And here's how I am trying to bind to that control
<custom:Matrix x:Name="customMatrix" DockPanel.Dock="Top" Title="{Binding Title}" ItemsList="{Binding Items}"/>
并且主页的代码隐藏是
//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();
}
两个 DependencyProperty
对于控件的标题
和 ItemsList
,我相信,创建了相同的方式。尽管如此,绑定可能不工作,因为 ItemsListChanged
事件不是由该绑定引发的。
所以,问题是我不能通过XAML绑定我的窗口的 ViewModel.Items
集合到控件的 ItemsList
集合。正在为一个控件中的集合创建 DependencyProperty
与 DependencyProperty
不同的一个简单的字符串 c> DependencyProperty
Both DependencyProperty
s for the control's Title
and ItemsList
are, I believe, created the same way. Nonetheless, the binding is probably not working as the ItemsListChanged
event is not raised by that binding.
So, the problem is that I cannot bind my window's ViewModel.Items
collection via XAML to the control's ItemsList
collection. Is creating a DependencyProperty
for a collection within a control any different from DependencyProperty
for a simple string
property?
推荐答案
c>注册。 协同方差不适用于通用名单
,即您不能这样做 -
Problem is in your DependencyProperty
registration. Co-variance is not applicable for generic lists
i.e. you cannot do this -
ObservableCollection<object> objects = new ObservableCollection<int>();
您已将DP的类型声明为 ObservableCollection< object>
,但绑定类型 ObservableCollection< int>
的列表
You have declared type of DP as ObservableCollection<object>
but binding it with list of type ObservableCollection<int>
.
您应该将DP的类型更改为ObservableCollection< int>
或将更改绑定集合类型更改为ObservableCollection< object>
。
public ViewModel()
{
Items = new ObservableCollection<object> { 1, 2, 3, 4, 5, 6};
}
public ObservableCollection<object> Items { get; set; }
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