Question

I am currently trying to figure out a binding solution in Silverlight 4.

I have an observable collection of items. I want to bind this to a ComboBox but only display the items that match a certain condition. For example group == “Test Group.” I have tried quite a few ways to make this work but haven’t had any success.

Answer 1

In the past I have used LINQ in an exposed property on the VM e.g:

    /// <summary>
    /// Get filtered results(by location)
    /// </summary>
    public ObservableCollection<SearchResultData> FilteredResults        {
        get
        {
            return new ObservableCollection<SearchResultData>(Results.Where(p => p.LocationId == CurrentLocation.Id));
        }
    }

Using this approach you will need to provide a notification when the underlying collection in the LINQ changes e.g:

    public ObservableCollection<SearchResultData> Results
    {
        get { return _results; }
        set
        {
            _results = value;
            NotifyOfPropertyChange(() => Results);
            NotifyOfPropertyChange(() => FilteredResults);
        }
    }