I have a scenario where I have a Dictionary(Of TextObject, ObservableCollection(Of TextObject), a Parent / Children structure. TextObject is a simple class that exposes a Text property.I also have two Listboxes. One Listbox is bound to the Dictionary Keys and the other is bound to the ObservableCollection associated with the selected Key in the first Listbox. If a Parent has no children (the ObservableCollection.Count = 0) then I would like to change the background of the ListBoxItem to red. I cannot get the Datatrigger binding to work. I can certainly accomplish this with code but I would rather use the Datatrigger if I can. Any help would be appreciated.
Below is the code behind and XAML for a sample application.
XAML
<Window x:Class="MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApplication1"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525"><Window.Resources><DataTemplate x:Key="TextBlockTemplate"><TextBlock Text="{Binding Text}"
/></DataTemplate><Style x:Key="TestStyle"><Setter Property="Control.Background" Value="LightBlue"/><Style.Triggers><DataTrigger Binding="{Binding Acronyms.Item[DataContext].Count}" Value="0"><Setter Property="Control.Background" Value="Red"/></DataTrigger></Style.Triggers></Style></Window.Resources><Grid><Grid.ColumnDefinitions><ColumnDefinition/><ColumnDefinition/></Grid.ColumnDefinitions><ListBox Name="lsbParents"
Height="200" Grid.Column="0"
ScrollViewer.VerticalScrollBarVisibility="Visible"
ItemTemplate="{StaticResource TextBlockTemplate}"
SelectionChanged="lsbParents_SelectionChanged"
ItemContainerStyle="{StaticResource TestStyle}"
ItemsSource="{Binding Path=Keys}"
/><ListBox Name="lsbChildren"
Height="200" Grid.Column="1"
ScrollViewer.VerticalScrollBarVisibility="Visible"
ItemTemplate="{StaticResource TextBlockTemplate}"
/></Grid></Window>Visual Basic
Imports System.Collections.ObjectModel
Imports System.ComponentModel
Class MainWindow
Dim _Dict1 As Dictionary(Of TextObject, ObservableCollection(Of TextObject)) _
= New Dictionary(Of TextObject, ObservableCollection(Of TextObject))(New TextObject.EqualityCompare)
Public Sub New()
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
CreateData()
Me.DataContext = Dict1
End Sub
Public ReadOnly Property Dict1() As Dictionary(Of TextObject, ObservableCollection(Of TextObject))
Get
Return _Dict1
End Get
End Property
Private Sub CreateData()
Dim Text1 As TextObject
Dim TextCol As ObservableCollection(Of TextObject)
For i As Integer = 1 To 5
Text1 = New TextObject("Parent " + i.ToString)
TextCol = New ObservableCollection(Of TextObject)
For j As Integer = 1 To 5 - i
TextCol.Add(New TextObject("Child " + j.ToString))
Next
_Dict1.Add(Text1, TextCol)
Next
End Sub
Private Sub lsbParents_SelectionChanged(sender As Object, e As SelectionChangedEventArgs)
lsbChildren.ItemsSource = _Dict1(CType(e.AddedItems(0), TextObject))
End Sub
End Class
Public Class TextObject
Implements INotifyPropertyChanged
Public Sub New(value As String)
_Text = value
End Sub
Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
Protected Sub OnPropertyChanged(ByVal Value As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(Value))
End Sub
Private _Text As String = ""
Public Property Text() As String
Get
Return _Text
End Get
Set(ByVal value As String)
_Text = value
OnPropertyChanged("Text")
End Set
End Property
Public Class EqualityCompare
Implements IEqualityComparer(Of TextObject)
Public Shadows Function Equals(x As TextObject, y As TextObject) As Boolean Implements IEqualityComparer(Of TextObject).Equals
Return x.Text = y.Text
End Function
Public Shadows Function GetHashCode(obj As TextObject) As Integer Implements IEqualityComparer(Of TextObject).GetHashCode
Return obj.Text.GetHashCode
End Function
End Class
End Class