Geek asks and answers

How can I link UIElement support?

DependencyProperties UIElementdo not support data binding (you get something like:

"Could not find governing FrameworkElement ..")

. If you try, you will get an error because WPF cannot resolve the DataContext. From what I know, you get a support binding if you inherit FrameworkElement or Freezable, but in this case I cannot just change the base class. Is there a way to get UIElement to support data binding?

I tried to add the DataContext property to the UIElement class as follows:

  FrameworkElement.DataContextProperty.AddOwner(typeof(Bitmap), new 
    FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.Inherits));

I also tried to bind by specifying "ElementName" in the binding expression, but I still cannot resolve the parent DataContext (I thought that binding explicitly ElementName would just eliminate the need to resolve the DataContext).

This is a binding. This class is called "Bitmap".

<Utils:Bitmap Source="{Binding Path=Icon}" />
<TextBlock Grid.Row="1" Grid.ColumnSpan="3" MaxWidth="90" Text="{Binding Path=Name}" TextWrapping="Wrap" TextAlignment="Center"/>

Text block binding works as expected, the first binding does not work. The linked view model has both properties (I am attached to the Image class before and worked).

The bitmap class can be found on this blog: http://blogs.msdn.com/b/dwayneneed/archive/2007/10/05/blurry-bitmaps.aspx

With some advanced binding diagnostics, I get this output:

System.Windows.Data Warning: 65 : BindingExpression (hash=14926099): Framework mentor not found
System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=Icon; DataItem=null; target element is 'Bitmap' (HashCode=117163); target property is 'Source' (type 'BitmapSource')
System.Windows.Data Warning: 63 : BindingExpression (hash=6195855): Resolving source  (last chance)
System.Windows.Data Warning: 65 : BindingExpression (hash=6195855): Framework mentor not found
System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=Icon; DataItem=null; target element is 'Bitmap' (HashCode=55762700); target property is 'Source' (type 'BitmapSource')
System.Windows.Data Warning: 63 : BindingExpression (hash=48657561): Resolving source  (last chance)
System.Windows.Data Warning: 65 : BindingExpression (hash=48657561): Framework mentor not found
System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=Icon; DataItem=null; target element is 'Bitmap' (HashCode=35264868); target property is 'Source' (type 'BitmapSource')
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3 answers

FrameworkElement, . , , , - H.B. , , FrameworkElement, , UIElement.

. http://msdn.microsoft.com/en-us/library/ms743618.aspx , (, UIElement FrameworkElement).

Update:

, MSDN ( ) , FrameworkElement, DependencyObject. , DataContext , ElementName .

, :

BindingOperations.SetBinding(MyBitmap, Bitmap.IconProperty, new Binding() { Source = this.DataContext /* Or any other source */, Path = new PropertyPath("Icon")});

RelativeSource ( FrameworkElement):

<Utils:Bitmap Source="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type FrameworkElement}}, Path=DataContext.Icon}" />
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{Binding Source={x:Reference elementName}} {Binding ElementName=elementName}.

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As already noted, you can contact any object that inherits from DependencyObject, if you want DataContext, I would suggest that you simply inherit the class from FrameworkElement. Even forms like Rectangle do this, if you have some control over the image, it makes sense to choose a higher level as the base class.

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