ICollectionView filtering issue

Question

i'm having a ICollectionView with filtering in colde. the problem is that the filtering never executes...

this is the code:

private ObservableCollection<string> _jobSizes;
private CollectionViewSource _jobSizesSource;


public ICollectionView JobSizesView
{
    get
    {
        if (_jobSizesSource == null)
        {
            _jobSizesSource = new CollectionViewSource
                {
                    Source = JobSizes
                };
        }

        _jobSizesSource.View.Filter = OnSizeFilter;
        return _jobSizesSource.View;
    }
}


private bool OnSizeFilter(object item)
{
    if (string.IsNullOrEmpty(_size))
        return true;

    if (((string) item).StartsWith(Size))
        return true;

    return false;
}

i use JobSizesView.Refresh(); to refresh the list... but also while constructing the list the filter is not executes...