Web Forms :: How To Synchronize Users Requests / Threads

I have what I consider a pretty complex situation that I am not sure if it can even be accomplished via an ASP.NET web application. (I am using aps.net 4.0) But what I want to do is design a "online auction site" that can handle many autions running at the same time. So I can only imagine eBay and all the other millions of auction sites out there are all doing this someway or another. My biggest concern is that I want to make sure the design here to make the site as effiecent as possible. Here is specifically what I am trying to figure out.

I think I need to create an object (per active auction) that stays in memory for the life of the auction. This object would have at least the following information:

Aution ID, time remaining, highest bidder id, bid price, Thread Control Variable, etc...

Now here is the tricky part that I think is vital for auction sites. Lets say you have 500 users on my website that are all watching the same auction and it is getting down to the last second of the auction and they all click to place a bid at the same time. Keep in mind this may also be at the same time hundreds of other users are placing bids for other auctions going on all at the same time.

How do I get all these requests (bids), for a single auction, lined up so that they are processed "one at a time"? But some how I need to be able to make all requests wait in a queue until it is their "turn" then I would need to be able to update the in memory object, write a record into a SQL database and then begin returning information back to each user.

Based on other development languages I have used in the past I know their were objects that I could create that could be used to get multiple threads to run in order (in other words syncronized). Usually it would be a case where I would be listening on a server socket and could do something like ThreadVariable.Lock, <process the request>, thenThreadVariable.Unlock. What that would do, is force all threads that tried to call ThreadVariable.Lock to wait until no other threads had the variable locked then it could proceed. Obviously the code it processes between the lock and unlock should be as quick and effecient as possible so it does not create a major traffic jam.

Because my thinking is this "object" I am referring to as being in memory, most likely will play a big role in answering the question about getting the requests in a "one at a time" situation it may be the focus of the question is more like how would I create "an object" and store it in memory to be quickly and easily accessed?

And even more generically does this even sound like I am on the right track

I think the topic of "communication to and from users" will need to be a completly different thread.