MSMQ querying for a specific message

I have a questing regarding MSMQ... I designed an async arhitecture like this:

CLient - >开发者_开发问答 WCF Service (hosted in WinService) -> MSMQ

so basically the WCF service takes the requests, processes them, adds them to an INPUT queue and returns a GUID. The same WCF service (through a listener) takes first message from queue (does some stuff...) and then it puts it back into another queue (OUTPUT).

The problem is how can I retrieve the result from the OUTPUT queue when a client requests it... because MSMQ does not allow random access to it's messages and the only solution would be to iterate through all messages and push them back in until I find the exact one I need. I do not want to use DB for this OUTPUT queue, because of some limitations imposed by the client...

You can look in your Output-Queue for your message by using

var mq = new MessageQueue(outputQueueName);
mq.PeekById(yourId);

Receiving by Id:

mq.ReceiveById(yourId);

A queue is inherently a "first-in-first-out" kind of data structure, while what you want is a "random access" data structure. It's just not designed for what you're trying to achieve here, so there isn't any "clean" way of doing this. Even if there was a way, it would be a hack.

If you elaborate on the limitations imposed by the client perhaps there might be other alternatives. Why don't you want to use a DB? Can you use a local SQLite DB, perhaps, or even an in-memory one?

Edit: If you have a client dictating implementation details to their own detriment then there are really only three ways you can go:

1. Work around them. In this case, that could involve using a SQLite DB - it's just a file and the client probably wouldn't even think of it as a "database".
2. Probe deeper and find out just what the underlying issue is, ie. why don't they want to use a DB? What are their real concerns and underlying assumptions?
3. Accept a poor solution and explain to the client that this is due to their own restriction. This is never nice and never easy, so it's really a last resort.

You may could use CorrelationId and set it when you send the message. Then, to receive the same message you can pick the specific message with ReceiveByCorrelationId as follow:

message = queue.ReceiveByCorrelationId(correlationId);

Moreover, CorrelationId is a string with the following format:

Guid()\\Number