How do I sort Lucene results by field value using a HitCollector?

I'm using the following code to execute a query in Lucene.Net

var collector = new GroupingHitCollector(searcher.GetIndexReader());
searcher.Search(myQuery, collector);
resultsCount = collector.Hits.Count;

How do I sort these search results based on a field?

Update

Thanks for your answer. I had tried using TopFieldDocCollector but I got an error saying, "value is too small or too large" when i passed 5000 as numHits argument value. Please suggest a valid value to pass.