More code from geekstream.devrexlabs.com

gistfile1.cs

private void RemoveFeedFromSearchIndex(Feed feed)
{
    var searchTermsToRemove = new List<string>();
    var itemsToRemove = new HashSet<FeedItem>(feed.Items);

    foreach (KeyValuePair<string, HashSet<IndexEntry>> kvp in _searchIndex)
    {
        var searchTerm = kvp.Key;
        var entrySet = kvp.Value;

        _statistics.TotalKeywords -= entrySet.RemoveWhere(entry => itemsToRemove.Contains(entry.Item));
        if (entrySet.Count == 0) searchTermsToRemove.Add(searchTerm);
    }
    _statistics.UniqueKeywords -= searchTermsToRemove.Count;

    foreach (string searchTerm in searchTermsToRemove) _searchIndex.Remove(searchTerm);
}