Search engine for .net

I am looking for a search engine that can be used for sites. Sometimes we dont want to use google embedded search or the complication of lucene.

I run in to these requests: Crawl based search Рейтинг и ранжирование контента на основе типов контента Searching documents like pdf and docs etc..

I dont mind if it is a commercial control that we have to purchase but I would like to be able to integrate it nicely in to some of these use cases