Combobox not updating when bound to CollectionViewSource which is then updated

Question

I have the following:

    <Window.Resources>
        <CollectionViewSource Source="{Binding Categories}" x:Key="Categories"/>
    </Window.Resources>
    ....    
    <ComboBox x:Name="cboCategory" Margin="170,125,0,0" ItemsSource="{Binding Source={StaticResource Categories}}" ItemTemplate="{StaticResource CategoryTemplate}" SelectedValue="{Binding Source={StaticResource Item}, Path=category}" SelectedValuePath="ID" Width="200" Style="{StaticResource RoundedComboBox}" HorizontalAlignment="Left" VerticalAlignment="Top"/>

Then in code

    Private _Categories As ObservableCollection(Of CategoryEntry)
    Public Property Categories As ObservableCollection(Of CategoryEntry)
        Get
            Return _Categories
        End Get
        Set(value As ObservableCollection(Of CategoryEntry))
            _Categories = value
        End Set
    End Property

    .....

    strSelect = "SELECT * FROM Categories WHERE Categories.comment<>'Reserved' ORDER BY Categories.comment"
    dsccmd = New OleDbDataAdapter(strSelect, cn)
    dsccmd.Fill(dsc, "Categories")
    dvc = New DataView(dsc.Tables("Categories"))
    _Categories = New ObservableCollection(Of CategoryEntry)(dvc.ToTable.AsEnumerable().[Select](Function(i) New [CategoryEntry](i("ID"), i("comment").TrimEnd(" "), i("work"), If(i("work"), New SolidColorBrush(Colors.CornflowerBlue), New SolidColorBrush(Colors.White)))))
    Me.DataContext = Me

This works fine. However if I change the contents of _Categories eg. using code as above setting _Categories = New ObservableCollection...... the combobox is not updated.

I have tried using CollectionViewSource.GetDefaultView.Refresh and ComboBox.UpdateLayout with no success

Help!

Thanks Andy

Kenneth · Accepted Answer · 2013-04-23T23:35:41.797

0

Your not actually updating your ObservableCollection, your just replacing it.

If you replace the reference you need to raise the propertychanged-event:

Private _Categories As ObservableCollection(Of CategoryEntry)
Public Property Categories As ObservableCollection(Of CategoryEntry)
    Get
        Return _Categories
    End Get
    Set(value As ObservableCollection(Of CategoryEntry))
        _Categories = value
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArg("Categories"))
    End Set
End Property

This is of course supposing that the class implements INotifyPropertyChanged

edited Apr 23 '13 at 23:35

answered Apr 23 '13 at 22:58

Kenneth

28,294
6
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Well if it "works" before it should have the INotifyPropertyChanged in it and the INotifyCollectionChanged should already be in ObservableCollection (hint the Observable in ObservableCollection) – Stelzi79 Apr 23 '13 at 23:11
Like I said, although the collection will notify the view when it gets updated. It will not notify the view if it gets replaced. He's creating a NEW observablecollection not changing the existing one. – Kenneth Apr 23 '13 at 23:22
It should be `PropertyChangedEventArgs("Categories")` without underscore. – LPL Apr 23 '13 at 23:33
Hi. I have added `Class ItemView Implements INotifyPropertyChanged Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged Private Sub NotifyPropertyChanged(ByVal info As String) RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(info)) End Sub` at the top of the module and added a `NotifyPropertyChanged("Categories")` in the property as you suggest above - doesn't work. Thanks. – Andy Powell Apr 23 '13 at 23:44

score 0 · Answer 2 · answered Apr 23 '13 at 23:06

0

Well that's usual behavoir of Bindings. If you "make" a new ObservableCollection you have to "make" a new binding to the new object because the binding was with a now defunct Object which you replaced with the new one you created before. Best thing to do is that you make a _Categories.Clear() and then add the content to it (with .AddRange(new ObservableCollection(...)) or such things).

answered Apr 23 '13 at 23:06

Stelzi79

585
3
12

Thanks. However I tried `_Categories.Clear() For Each c As CategoryEntry In New ObservableCollection(Of CategoryEntry)(dvc.ToTable.AsEnumerable().[Select](Function(i) New [CategoryEntry](i("ID"), i("comment").TrimEnd(" "), i("work"), If(i("work"), New SolidColorBrush(Colors.CornflowerBlue), New SolidColorBrush(Colors.White))))) _Categories.Add(c) Next` and it didn't work – Andy Powell Apr 23 '13 at 23:40

Combobox not updating when bound to CollectionViewSource which is then updated

2 Answers2