UPDATE: The calendar is full. You can sign up to be an alternate, in case someone drops out or fails to deliver. I can't give you a date though, so you'd essentially have to have a post ready to go as soon as December 1st. And please, don't let the lack of an advent date keep you from writing that C# blog post! Finally, due to the tremendous response, I will double up the slots next year (from 25 to 50), assuming this advent goes well :)
I heard about the F# Advent Calendar, a traditional that's been carried on since 2010 (2014 in English). I think this is a great idea, and there needs to be one for C# too!
Reserve a slot on Twitter (with hash tag #csadvent) or leave a comment on this post. You do not have to announce your topic until the day you reserve.
Prepare a blog post (in English).
Add a link in your blog post that links back to here, so that your readers may find the entire advent.
Publish your blog post on the specified date. Your post must be related to C# in some way, but otherwise the content is completely up to you. I've posted a few ideas below to get your creativity flowing.
Post the link to your post on Twitter with hashtags #csharp and #csadvent
Below are all the slots, and who has claimed each date. I chose to go with 25 total slots (yes I know some advent calendars are 24).
I will do my best to keep this up to date. The slots will be first come first serve. I have already claimed December 25th for myself, since I assume that will be the least desirable date. But I'm happy to swap if you really really want that day.