How many genes does C. elegans have?

I am doing enrichment analysis for some lists of C. elegans microarray data, I need a background, ie the number of all the C. elegans genes ( in the current release maybe).
It is probably documented somewhere in Wormbase but I could not find it.

Thanks for suggestions.

Each release of WormBase has a set of accompanying release notes which has some of the information that you are after:

Of course, the first problem is that you might want to clarify what you mean by a gene. Only-protein coding? RNA genes? Pseudogenes? Non-overlapping isoforms etc.

Thanks for your quick reply.
Yes. I was reading this already.
And what you say is exactly the question I have. For gene expression microarray analysis, could I use this # 24247 based on "Gene <-> CDS,Transcript,Pseudogene connections

Caenorhabditis elegans entries with WormBase-approved Gene name 24247"?

I think that includes many RNA genes and refers to those genes for which the CGC has given a 3 or 4 letter name. There still might be valid genes in WormBase which have not yet (or are in the process) of getting CGC names. The release notes imply there are 20,316 protein-coding genes (not counting alternative splice isoforms).