ListBox checkbox command binding

Question

I can't figure this out. I thought I had the binding set properly but it's not firing. So I have a View:

<ListBox x:Name="EquipmentViewsListBox"
         ItemsSource="{Binding EquipmentViews, UpdateSourceTrigger=PropertyChanged}"
         SelectionMode="Extended"
         BorderThickness="0"
         Height="150"
         Margin="5,5,10,10">
    <ListBox.ItemContainerStyle>
        <Style TargetType="ListBoxItem">
            <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
        </Style>
    </ListBox.ItemContainerStyle>
    <ListBox.ItemTemplate>
        <DataTemplate>
            <CheckBox IsChecked="{Binding IsSelected, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" 
                      Command="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=ListBox}, Path=DataContext.ViewSelected}" 
                      CommandParameter="{Binding RelativeSource={RelativeSource Self}}" 
                      Content="{Binding Name}"/>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

I want to fire a command every time the checkbox in that ListBox is selected. I created a command on my view model like so:

public class SdddViewModel : ViewModelBase
{
    public SdddModel Model { get; set; }
    public RelayCommand<ViewWrapper> ViewSelected { get; set; }

    public SdddViewModel(SdddModel model)
    {
        Model = model;
        ViewSelected = new RelayCommand<ViewWrapper>(OnViewSelected);
    }

    private void OnViewSelected(ViewWrapper obj)
    {
        var asd = obj;
    }
}

So I understand that when I do a ListBox.ItemTemplate the context for that item becomes the ListBoxItem so in my case a class object ViewWrapper. That works fine with the Name binding for content as well with the IsSelected property. It's the command that is not firing when item is checked. I set the relative ancestor to ListBox and the Path=DataContext but still nothing happens. Ideas?

TomerAgmon1 · Accepted Answer · 2018-03-04 16:49:31Z

2

The problem is that the CommandParameter doesn't match. You Declared it so the CommandParameter is ViewWrapper but you sent a parameter of type CheckBox by using RelativeSource Self. Change the CommandParameter to simply {Binding} which means it sends the DataContext of the ListBoxItem, which is ViewWrapper.

You could have detected this binding error using Snoop.

answered Mar 4, 2018 at 16:49

TomerAgmon1

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2 Comments

konrad Over a year ago

Dude, you are a genius! So I was at least expecting the stack trace to throw up an exception or something instead it was just doing nothing. I am installing Snoop now. Thanks a lot.

TomerAgmon1 Over a year ago

Binding errors don't throw exceptions but you can also see them in the Output window...but yeah, Snoop is a must

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