I have a custom UserControl called ReferencedItem
. It should take a Guid called ItemId. It is implemented as such:
private static void OnItemIdChanged(DependencyObject dobj, DependencyPropertyChangedEventArgs dpArgs)
{
//Do something
}
public static readonly DependencyProperty ItemIdProperty = DependencyProperty.Register("ItemId", typeof(Guid?), typeof(ReferencedItem), new FrameworkPropertyMetadata(
// use an empty Guid as default value
Guid.Empty,
// tell the binding system that this property affects how the control gets rendered
FrameworkPropertyMetadataOptions.AffectsRender,
// run this callback when the property changes
OnItemIdChanged
));
public Guid? ItemId
{
get { return (Guid?)GetValue(ItemIdProperty); }
set { SetValue(ItemIdProperty, value); }
}
public ReferencedItem()
{
InitializeComponent();
ViewModel = new ReferencedItemCtrlViewModel();
DataContext = ViewModel;
}
The ItemsSource
will be made up of Reference
objects defined as:
public class Reference
{
public Guid Id { get; set; }
}
Now when binding this ReferencedItem
the value is not set as intended. Here is the code I want to work, but does not bind as intended:
<ItemsControl x:Name="ReferenceStack" ItemsSource="{Binding References}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Vertical"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<local:ReferencedItem ItemId="{Binding Id}" Height="30" HorizontalAlignment="Stretch" VerticalAlignment="Top"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
I have tried:
<local:ReferencedItem ItemId="128d48f0-f061-49fb-af49-b8e4ef891d03" Height="30" HorizontalAlignment="Stretch" VerticalAlignment="Top"/>
This works as expected, the OnItemIdChanged
method is triggered.
<Label Content="{Binding Id}" HorizontalAlignment="Left" VerticalAlignment="Top" Height="30" Width="90"/>
This works as expected, a label is rendered with the Id.
Is there something I'm missing here? From what I can tell the data is available at bind time -- it just doesn't bind under the exact conditions I need it to :)
Thanks for any input!
EDIT:
Here is the code-behind for ReferencedItemList
, the first block of XAML posted above:
public partial class ReferencedItemList : UserControl
{
protected ReferencedItemListCtrlViewModel ViewModel;
public ReferencedItemList()
{
InitializeComponent();
ViewModel = new ReferencedItemListCtrlViewModel();
DataContext = ViewModel;
}
public void Load(Guid id, string name)
{
ViewModel.Load(id, name);
//ReferenceStack.ItemsSource = ViewModel.References;
}
}
The commented line has been experimented with in place of the ItemsSource="{Binding References}"
that was defined in the XAML.
I don't think I can successfully post the code for ReferencedItemListCtrlViewModel
without going down a rabbit hole -- needless to say it has a property References
of type ObservableCollection<Reference>
where Reference
is defined earlier in this post.
ReferencedItem.xaml:
<v:BaseUserControl.Resources>
<BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter" />
</v:BaseUserControl.Resources>
<StackPanel Orientation="Horizontal">
<Image x:Name="LinkIcon" Visibility="{Binding HasReference, Converter={StaticResource BooleanToVisibilityConverter}}" ToolTip="View Referenced Item" Source="/Images/link.png" Height="18" MouseUp="LinkIcon_MouseUp"/>
<TextBlock x:Name="ReferencedObjectDesc" Text="{Binding ReferenceHierarchy}" FontStyle="Italic" VerticalAlignment="Center" />
</StackPanel>
I just wanted to post the answer (explanation) I came across.
The problem was changing the DataContext of my ReferencedItem
user control in the constructor. The view would instantiate a ReferencedItem
and alter the DataContext - so once it was time to bind I had already flipped the context from the intended Reference
.
There are multiple ways to resolve the timing - all project dependent. Either avoid setting the DataContext all together, set it post binding, or change the context on other items as appropriate.
Much thanks to Sinatr , Andrew Stephens , and Mike Strobel for all mentioning this at one point or another -- just took me some time to actually reach it. I don't think there's a way to assign credit to a comment, but let me know if there is.
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.