Question

I have a wpf, mvvm app, using the catel (http://catel.codeplex.com) framework\toolkit, C# .Net 4.0. The app has a ListBox with a TextBlock and ComboBox. The ListBox and ComboBox are populated from 2 different ObservableCollection from the ViewModel. I need to save (to a db), when the user clicks a button, each row in the ListBox where the user has selected an item from the ComboBox. The SelectionChanged event does not fire for any of the ComboBoxes in the ListBox. The idea being that I add to a list (ArrayList or IList?), in the ViewModel, each time the user selects an item in a ComboBox and for what row the item has been selected.

Or am I going about this the wrong way by trying to use the ComboBoxe SelectionChanged event? I also tried iterating thru the ListBox.Items but this seems like a hak and I want to avoid ui element logic in the ViewModel if possible.

The xaml:

<Grid>
<StackPanel Orientation="Horizontal">
    <Label Width="180">Field1</Label>
    <ListBox Height="200" 
            IsSynchronizedWithCurrentItem="True" 
            ItemsSource="{Binding List1, Mode=OneWay}" 
            Name="listBox1" 
            SelectionMode="Single" 
            Width="300">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <StackPanel Orientation="Horizontal" Width="290">
                    <TextBlock Width="90" Text="{Binding}"></TextBlock>
                        <ComboBox Width="180" ItemsSource="{Binding DataContext.List2, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}" DisplayMemberPath="Field1">
                            <i:Interaction.Triggers>
                                <i:EventTrigger EventName="SelectionChanged">
                                    <catel:EventToCommand Command="{Binding SelectionChangedCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ItemsControl}}}" DisableAssociatedObjectOnCannotExecute="False" PassEventArgsToCommand="True" />
                                </i:EventTrigger>
                            </i:Interaction.Triggers>
                        </ComboBox>
                    </StackPanel>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</StackPanel>

ViewModel code:

//in the ViewModel constructor

SelectionChangedCommand = new Command<SelectionChangedEventArgs>(OnSelectionChangedCommandExecute, OnSelectionChangedCommandCanExecute);



public Command<SelectionChangedEventArgs> SelectionChangedCommand { get; private set; }

private bool OnSelectionChangedCommandCanExecute()
{
    return true;
}

private void OnSelectionChangedCommandExecute(SelectionChangedEventArgs e)
{
    // add or update list....
}

Answer 1

In Command binding you have used binding which has relative source binding…

consider making these changes in binding

1) using list box as Ancestortype

2) While binding use Path=DataContext.SelectionChangedCommand otherwise it will take list box as datacontext.

<catel:EventToCommand Command="{Binding Path=DataContext.SelectionChangedCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ListBox}}}" DisableAssociatedObjectOnCannotExecute="False" PassEventArgsToCommand="True" />