I need to build full-text search functionality into our knowledge base system using C#. How do I start?
For example from Lucene:
http://lucene.apache.org/java/docs/
C# port is here http://incubator.apache.org/lucene.net/
You should also read something about the the information retrieval, and you can start with this one : http://www.amazon.com/Modern-Information-Retrieval-Ricardo-Baeza-Yates/dp/020139829X
You will probably need an indexing facility if your text base is non trivial.
I use Lucene.Net in my open source bug tracking application, BugTracker.NET. Download it and look at my_lucene.cs - which does the indexing - and search_text.aspx - which does the searching. I went from knowing nothing about Lucene to being able to integrate it into my app in just a weekend.
I explain it here:
http://www.ifdefined.com/blog/post/2009/02/Full-Text-Search-in-ASPNET-using-LuceneNET.aspx