I have the following scenario:
XAML:
<ListView Name="lsv_edit_selectNode" Grid.Row="2" Grid.Column="0" Grid.ColumnSpan="4"
Grid.RowSpan="17" IsSynchronizedWithCurrentItem="True" SelectionMode="Single"
ItemsSource="{Binding Path=Nodes.CollectionView, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnNotifyDataErrors=True}">
Where Nodes is a custom ObservableCollection
that contains a ListCollectionView:
Public Class FilterableObservableCollection(Of T)
Inherits ObservableCollection(Of T)
Implements INotifyPropertyChanged, INotifyCollectionChanged
Public Property CollectionView As ListCollectionView
Get
Return _collectionView
End Get
Protected Set(value As ListCollectionView)
If value IsNot _collectionView Then
_collectionView = value
NotifyPropertyChanged()
End If
End Set
End Property
'etc.
T
in this case is a Node
object, with many properties including the one I'm interested in (call it NodeResults):
Public Class Node
Inherits ObservableValidatableModelBase
Public Property NodeResults as NodeResults
Set
SetAndNotify(_nodeResults, Value) ' INotifyPropertyChanged
AddHandler _nodeResults.ErrorsChanged, AddressOf BubbleErrorsChanged ' INotifyDataErrorInfo?
End Set
End Property
' etc.
and NodeResults
:
Public Class NodeResults
Inherits ObservableValidatableModelBase
' many properties here, each validated using custom Data Annotations. This works, when I bind a text box directly to here, for example.
ObservableValidatableModelBase
Implements INotifyDataErrorInfo
, and stores its errors in a collection called errors
:
Private errors As New Dictionary(Of String, List(Of String))()
Public ReadOnly Property HasErrors As Boolean Implements INotifyDataErrorInfo.HasErrors
Get
Return errors.Any(Function(e) e.Value IsNot Nothing AndAlso e.Value.Count > 0)
End Get
End Property
Public Function GetErrors(propertyName As String) As IEnumerable Implements INotifyDataErrorInfo.GetErrors
Try
If Not String.IsNullOrEmpty(propertyName) Then
If If(errors?.Keys?.Contains(propertyName), False) _
AndAlso If(errors(propertyName)?.Count > 0, False) Then ' if there are any errors, defaulting to false if null
Return errors(propertyName)?.ToList() ' or Nothing if there are none.
Else
Return Nothing
End If
Else
Return errors.SelectMany(Function(e) e.Value.ToList())
End If
Catch ex As Exception
Return New List(Of String)({"Error getting errors for validation: " & ex.Message})
End Try
End Function
Public Event ErrorsChanged As EventHandler(Of DataErrorsChangedEventArgs) Implements INotifyDataErrorInfo.ErrorsChanged
Public Sub NotifyErrorsChanged(propertyName As String)
ErrorsChangedEvent?.Invoke(Me, New DataErrorsChangedEventArgs(propertyName))
End Sub
Public Sub BubbleErrorsChanged(sender As Object, e As DataErrorsChangedEventArgs)
If TypeOf (sender) Is ObservableValidatableModelBase Then
errors = DirectCast(sender, ObservableValidatableModelBase).errors
End If
NotifyErrorsChanged(String.Empty)
End Sub
What I want to happen is for the individual Node
s in the CollectionView
to notify the ListView
, so that it highlights the individual entries that are invalid (i.e. have a NodeResults
that is invalid) on the screen.
My first instinct is that Node somehow needs to subscribe to and bubble the NodeResults
' ErrorsChanged
event, hence the BubbleErrorsChanged
method on the ObservableValidatableModelBase
class - but that doesn't seem to work.
Another possibility is - does ListView even have a default template for displaying validation exceptions? If not, should something like this work? (it doesn't...)
<ListView.ItemContainerStyle>
<Style TargetType="ListViewItem">
<Setter Property="Background" Value="{Binding Path=(Validation.Errors).CurrentItem, Converter={StaticResource ValidationExceptionToColourConverter}}"/>
</Style>
</ListView.ItemContainerStyle>
Where ValidationExceptionToColourConverter
simply returns Brushes.Red or Brushes.White depending on whether the error is Nothing
or not.
Note: Binding a text box directly to Nodes.NodeResults.SomeProperty works fine, giving the results I'm expecting.
I needed the following:
<ListView.ItemContainerStyle>
<Style TargetType="ListViewItem">
<Setter Property="Background" Value="{Binding Path=HasErrors, Mode=OneWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource BooleanToBrushConverter}}"/>
</Style>
</ListView.ItemContainerStyle>