Question

Ok, this has been a head scratcher for me. I have a ListBox I am binding to a linq query like so:

    private IQueryable<Feed> _feeds;

    public IQueryable<Feed> Feeds
    {
        get
        {
            if (_feeds == null)
            {
                var feedsQuery = from f in _db.Feed orderby f.Title select f;
                _feeds = feedsQuery;
            }
            return _feeds;
        }
    }

    public Options()
    {
        InitializeComponent();
        this.DataContext = Feeds;
    }

(For the record I’ve also tried List, instead of IQueryable)

Everything shows up great and I have a databound form that allows you to edit a record and all of those changes work just fine, the modified data shows up in the list.

The problem comes with I add an item. Nothing shows up in the list. The data goes into the database fine, but the only way to see the data is closing and restarting my app. I’m using the code below as an example:

        Feed feed = new Feed()
        {
            ID = Guid.NewGuid(),
            Url = "http://www.test.com",
            Title = "Test"
        };
        _db.Feed.InsertOnSubmit(feed);
        _db.SubmitChanges();
        _db.Refresh(System.Data.Linq.RefreshMode.OverwriteCurrentValues);

(with or without the _db.Refresh nothing happens)

What’s going on?

Answer 1

You are doing everything right, you jus need to use ObservableCollection. This will notify the ListBox about any changes in the list and refresh it automatically.

From MSDN

In many cases the data that you work
with is a collection of objects. For
example, a common scenario in data
binding is to use an ItemsControl
such as a ListBox, ListView, or
TreeView to display a collection of
records.

P.S. you don’t need a db refresh