Streaming an undetermined number of objects through WCF

I have a WCF service that needs to read large (10 to 20 million) numbers of objects from the database.

What I'd like to do, is have the client open up a stream and have the server push data from the database as it's reading.

So the client could just sit in a loop deserializing messages开发者_如何学C until it gets the EOF message from the server, in the style of the Twitter Streaming API, but with a finite set. The issue I'm having, is how to return the stream and then keep writing to it. Is this possible with WCF?

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How about instead of setting up a streaming/blocking service you use something like WS Dual Http. With it you have an async bidirectional callback channel that allows you to request/reply information back and forth between the server and the client. Issues you may see if you want to stream the entire set is a normal fashion is that some of the resources may block other requests (or timeout) while other users try to access the service.

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The problem is that WCF does not provide response stream to operation. The stream returned from operation is just a "content" of some message. I tryed to trick WCF with some threading scenarios where I returned MemoryStream and tryed to fill it from other thread but as expected it didn't work.

Mentioned HttpHandler is the only way to go.

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You might want to take a look at the PollingDuplexHttpBinding (notice id did may might :-)).

Some aren't very fond of this binding but I haven't had too much trouble with it after the initial hurdle of getting the config right.

It could certainly do the job I think since it's little more than the 'long polling trick' used in web-sockets as I understand.

HTH.