Question

How do I bind my button outside my binded ListBox?

This Listbox contains my search results and each search results has an “X” button that should delete the search history item.

Here’s a preview of my listbox

“X” Button only appears when I hover to an item

Here’s my XAML

<ListBox x:Name="listHistory" ItemsSource={Binding SearchHistory.SearchHistory} BorderThickness="0" Margin="0" Padding="0" HorizontalContentAlignment="Stretch">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <Grid>
                <!-- this binds to a string in ObservableCollection<string> -->
                <TextBlock Text="{Binding }" />

                <!-- this should bind to SearchHistory.Command_DeleteHistoryItem -->
                <!-- currently, this Command="{Binding SearchHistory.Command_DeleteHistoryItem}" doesn't work
                     System.Windows.Data Error: 40 : BindingExpression path error: 'SearchHistory' 
                     property not found on 'object' ''String' (HashCode=-1127982548)'. 
                     BindingExpression:Path=SearchHistory.Command_DeleteHistoryItem; 
                     DataItem='String' HashCode=-1127982548); 
                     target element is 'Button' (Name=''); 
                     target property is 'Command' (type 'ICommand')
                -->
                <Button Command="{Binding SearchHistory.Command_DeleteHistoryItem}" Grid.Column="1" HorizontalAlignment="Right" x:Name="btnDeleteHistoryItem" Content="r" FontFamily="Marlett" Style="{DynamicResource ButtonStyle}" Visibility="Hidden" Opacity="0.75" />
            </Grid>

            <DataTemplate.Triggers>
                <Trigger Property="IsMouseOver" Value="True">
                    <Setter Property="Visibility" TargetName="btnDeleteHistoryItem" Value="Visible" />
                </Trigger>
            </DataTemplate.Triggers>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

and here’s my ViewModel

public class ViewModel_SearchHistory : ViewModelBase
{
    ObservableCollection<string> _SearchHistory = new ObservableCollection<string>();
    public ObservableCollection<string> SearchHistory
    {
        get { return this._SearchHistory; }
        set
        {
            if (this._SearchHistory != value)
            {
                this._SearchHistory = value;
                base.RaisePropertyChanged("SearchHistory");
            }
        }
    }

    public ViewModel_SearchHistory()
    {
        this.Command_DeleteHistoryItem = new RelayCommand(DeleteHistoryItem);
    }

    public ICommand Command_DeleteHistoryItem
    {
        get;
        internal set;
    }

    public void DeleteHistoryItem()
    {
        Debug.WriteLine("blah");
    }
}

Problem there is this error

“System.Windows.Data Error: 40 : BindingExpression path error:
‘SearchHistory’ property not found on ‘object’ ”String’
(HashCode=-1127982548)’.
BindingExpression:Path=SearchHistory.Command_DeleteHistoryItem;
DataItem=’String’ (HashCode=-1127982548); target element is ‘Button’
(Name=”); target property is ‘Command’ (type ‘ICommand’)”

This tells me that, WPF is looking for SearchHistory.Command_DeleteHistoryItem in ObservableCollection<string> SearchHistory.. But NO, I have to bind the command in my ViewModel, and not in ObservableCollection<string> SearchHistory

I was thinking to have a new Model like this

public class Model_HistoryItemDetail
{
    public string Item { get; set; }
    public ICommand Delete { get; internal set; }

    public Model_HistoryItemDetail()
    {
        this.Delete = new RelayCommand(DeleteItem);
    }

    public void DeleteItem()
    {
    }
}

and in my SearchHistory ObservableCollection like this

ObservableCollection<Model_HistoryItemDetail> _SearchHistory = new ObservableCollection<Model_HistoryItemDetail>();
public ObservableCollection<Model_HistoryItemDetail> SearchHistory
{
    get { return this._SearchHistory; }
    set
    {
        if (this._SearchHistory != value)
        {
            this._SearchHistory = value;
            base.RaisePropertyChanged("SearchHistory");
        }
    }
}

The problem now is, how do I delete the item if I did that way?

---

So what’s the best way to do it?

Answer 1

<Button Command="{Binding DataContext.Search.Command_DeleteHistoryItem,RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ListBox}}}"/>

You need to use RelativeSource in order to climb up the Visual Tree and get a reference to the ListBox itself, then you can get its DataContext, which should be your ViewModel.