Updating listbox data with RaisePropertyChanged

Question

Hi!

In my silverlight app i have a view with a listbox:

<ListBox Canvas.Left="12" Canvas.Top="72" Height="468" Name="invoiceList" Width="453" ItemsSource="{Binding ElementList}" >
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}" />
                </DataTemplate>
            </ListBox.ItemTemplate>
</ListBox>

which is bound to the list of elements in my VM. The problem is that when I add new elements, one by one, using Relay Command:

public RelayCommand<Element> AddNewElement = new RelayCommand<Element>(NewElement(element));

   public void NewElement(Element element)
    {
        if(ElementList == null) ElementList = new List<Element>();
        if (element != null) ElementList.Add(element);
        RaisePropertyChanged("ElementList");
    }

the listbox updates only once, i.e. it shows only first element of the collection , though more items are inside ElementList

Answer 1

You need to bind to a list of type ObservableCollection then every update to the list collection will trigger the binding to update.

Example on how to create an observable collection of your list:

public ObservableCollection<string> MyElements { get; set; }
public void FillList()
{
    List<string> testList = new List<string>() {"string1", "string2"};
    MyElements = new ObservableCollection<string>(testList);
}

MyElements.Add("string3") will trigger binding to update

EDIT: I added a working example, I provide the xaml and ViewModelCode with the use of acommand to add some strings:

xaml:

<ListBox ItemsSource="{Binding MyStrings}"  />
<Button Command="{Binding AddExtraStringCommand}" Content="Add ExtraString" />

viewmodel.cs

public class Window1ViewModel : ViewModelBase
{
    public ObservableCollection<string> MyStrings { get; set; }
    public RelayCommand AddExtraStringCommand { get; set; }

    public Window1ViewModel()
    {
        patient = new Patient() { BirthdayString = "21/11" };
        MyStrings = new ObservableCollection<string>() { "string1", "string2", "string3" };
        AddExtraStringCommand = new RelayCommand(AddExtraString);
    }

    public void AddExtraString()
    {
        MyStrings.Add("nog enen extra om: " + DateTime.Now);
    }
}

I don't have to trigger the RaisePropertyChanged to make it work. Maybe you can check your code to this code example.