Binding ComboBox in ListBox

Question

I cant figure this one out. If I just have the combo-box by itself not embedded in a list box it will populate and selected the values I need.

The XAML

<ComboBox Name="comboBox1" 
          Height="23" 
          DataContext="{Binding Combox}" 
          ItemsSource="{Binding Comboxes}" 
          DisplayMemberPath="PV" 
          SelectedValuePath="PK"                  
          SelectedItem="{Binding SelectedItem}"
          VerticalAlignment="Top" 
          Width="120" />

The Code Behind

    public MainWindow()
    {
        InitializeComponent();

        DataAttribute d = new DataAttribute(2, "blue");

        Combox c = new Combox();

        c.SelectedItem = d;
        c.Comboxes.Add(new DataAttribute(1, "red"));

        c.Comboxes.Add(new DataAttribute(3, "Black"));
        c.Comboxes.Add(c.SelectedItem);

        comboBox1.DataContext = c;
    }

Class for holding data

public class Combox: INotifyPropertyChanged
{
    public Combox()
    {
        Comboxes = new List<DataAttribute>();            
    }

    private DataAttribute _selectedItem;// = new DataAttribute(-1, "NA");

    public List<DataAttribute> Comboxes { get; set; }

    public event PropertyChangedEventHandler PropertyChanged;

    public DataAttribute SelectedItem
    {
        get { return _selectedItem; }
        set
        {
            if (_selectedItem == value) return;
            _selectedItem = value;
            OnPropertyChanged("SelectedValue");
        }
    }

    private void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }        
}

public class DataAttribute
{
    public DataAttribute() { }

    public DataAttribute(int pk, string pv)
    {
        PK = pk;
        PV = pv;
    }

    public int PK { get; set; }
    public string PV { get; set; }

    public override string ToString()
    {
        return PV;
    }
}

All that works fine, but as soon as I try to create a list of com boxes in the listbox nothing. I can see the combo but no data. How on earth to you bind to it is XAML?

    public MainWindow()
    {
        InitializeComponent();

        List<Combox> com = new List<Combox>();
        DataAttribute d = new DataAttribute(2, "blue");

        Combox c = new Combox();

        c.SelectedItem = d;
        c.Comboxes.Add(new DataAttribute(1, "red"));

        c.Comboxes.Add(new DataAttribute(3, "Black"));
        c.Comboxes.Add(c.SelectedItem);

        com.Add(c);

        lstTest.ItemSource = com;
    }

As here is the XAML with a listbox. It no longer binds...

    <ListBox Name="lstTest" ItemsSource="{Binding}">        
        <ListBox.ItemTemplate>
            <DataTemplate>
                <ComboBox Name="comboBox1" 
                      DataContext="{Binding Combox}" 
                      ItemsSource="{Binding Comboxes}" 
                      DisplayMemberPath="PV" 
                      SelectedValuePath="PK"                  
                      SelectedItem="{Binding SelectedItem}"
                      VerticalAlignment="Top" 
                      Width="120" />        
            </DataTemplate>
        </ListBox.ItemTemplate>            
    </ListBox>

I am stumped as it was hard enough trying to figure out how to just get the selected object to appear without the list-box...

Maybe this link will be useful. I did that and it works. stackoverflow.com/questions/2695954/… — kam lung chan
– kam lung chan, Commented Jul 11, 2013 at 14:22

brunnerh · Accepted Answer · 2011-09-15 08:12:43Z

1

Inside the items of an ItemsControl the DataContext is the currectly templated item, if you want to get to a list that is to be used as the ItemsSource for the ComboBoxes you normally need to modify the bindings to use another source, e.g. RelativeSource or ElementName. (This is the case for one list that is to be used for all ComboBoxes)

In this case, where the list seems to be part of the item, you should only need to remove the binding on the DataContext as the DataContext is already the item (an instance of Combox).

edited Sep 15, 2011 at 8:12

answered Sep 15, 2011 at 8:01

brunnerh

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