Question

I bound (at least i think i did) data to a ListBox following a tutorial. The class element I want bound has data in it but i see nothing on the ListBox after some event. I have the following partial XAML:

 <ListBox x:Name="jukeBoxListBox" Height="227" VerticalAlignment="Top" ItemsSource="{Binding FilePathList}"/>

In the WPF form cs file I have. Should i set to class FolderItems or its attr filePathList? Also should I use ObservableCollection instead of list?

InitializeComponent();    
FolderItems folderItems = new FolderItems();
this.DataContext = folderItems.FilePathList;

My data class:

class FolderItems : INotifyPropertyChanged
{
    #region INotifyPropertyChanged implementation

    public event PropertyChangedEventHandler PropertyChanged;

    protected void Notify(string propertyName)
    {
        if (this.PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    #endregion INotifyPropertyChanged implementation

    private ObservableCollection<String> _pathList = new ObservableCollection<string>();

    public ObservableCollection<String> FilePathList
    {
        get { return _pathList; }
        set
        {
            if (value != _pathList)
            {
                _pathList = value;
                Notify("FilePathList");
            }
        }
    }
}

I think I need to mention that I change the List elements in a Button click event. Maybe the below is a part of the problem.

//in the event fItems is an instance of FolderItems   
var files = new ObservableCollection<string>();
ProcessFiles(of.SelectedPath, files);
fItems.FilePathList = files;
//...

    private void ProcessFiles(string path, ICollection<string> files)
    {
        foreach (var file in Directory.GetFiles(path).Where(name => name.EndsWith(".mp3", StringComparison.OrdinalIgnoreCase)))
            files.Add(file);    

        foreach (var directory in Directory.GetDirectories(path))
            ProcessFiles(directory, files);

    }

I hail from Javaland and am brand new to C#. Please excuse my language.

Answer 1

If you’d change List<string> to ObservableCollection<string> (see here), your binding would get notified about changes in the list, e.g. when you add items.

Also, you must change the property name in the Notify call to filePathList.

And you should follow coding conventions for properties in .Net, which are usually written with a leading uppercase character. So your property would be FilePathList.

private ObservableCollection<String> pathList = new ObservableCollection<string>();

public ObservableCollection<String> FilePathList
{
    get { return pathList; }
    set
    {
        if (value != pathList)
        {
            pathList = value;
            Notify("FilePathList"); // changed here
        }
    }
}

Change the binding to the renamed property:

<ListBox ... ItemsSource="{Binding FilePathList}"/>

---

See also Binding to Collections and Using Collection Objects as a Binding Source.

---

UPDATE

Your ProcessFiles method should be written as shown below to enable recursion.

private void ProcessFiles(string path, ICollection<string> files)
{
    foreach (var file in Directory.GetFiles(path).Where(name => name.EndsWith(".mp3", StringComparison.OrdinalIgnoreCase)))
    {
        files.Add(file);
    }

    foreach (var directory in Directory.GetDirectories(path))
    {
        ProcessFiles(directory, files);
    }
}

And be called like this:

var files = new ObservableCollection<string>();
ProcessFiles(of.SelectedPath, files);

var folderItems = new FolderItems();
folderItems.FilePathList = files;
DataContext = folderItems;

Or if you need to access the FolderItems object later (perhaps in some event handler) you might get it back from the DataContext:

DataContext = new FolderItems();

...

var folderItems = DataContext as FolderItems;
ProcessFiles(of.SelectedPath, folderItems.FilePathList);