Lucene.Net.Store.AlreadyClosedException: this IndexReader is closed - during shutdown

[Shazwazza]

When running under stress tests that shuts down the appdomain very often while also trying to view search results, an exception may occur:

Lucene.Net.Store.AlreadyClosedException: this IndexReader is closed

This is because when the app domain is shutdown, the reader is closed, but at the same time another request might still be iterating it. So we need to only close the reader at the last possible moment just before the appdomain terminates.