How to know when Lucene Index generation process is completed

I've a .net windows service which generates Lucene search indexes every night. I first get all the records from the database and add it to Lucene index using IndexWriter's AddDocument method and then call Optimize method before returning from the method. Since the records fetched are faily large, indexing takes around 2-3 minutes to complete. As you already know,Lucene generates intermediate segment files while it is generating the index and it compresses the whole index into 3 files when Optimize is called. Is there anyway I can know that this index generation process is finished by Lucene and index is avaialable for search? I need to know this because I want to call another method when process is completed.