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Asked: 2026-06-02T21:35:42+00:00

Possible Duplicate: WCF Duplex – Push different notifications to each client? I am designing

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Possible Duplicate:
WCF Duplex – Push different notifications to each client?

I am designing a 2 WCF services that all my clients will connect to.
One of these services will be a notifications service.

I would like each client to connect to the service, subscribe to it and then receive notifications, using a duplex Callback interface (the service will fire the ‘Notify’ operation in the clients).

This is my Design Idea:

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My question is:
When each client connects to my service, I will validate it against the ‘Users’ table in my database (I will be using a UserNamePasswordValidator and implement the ‘Validate’
function).

Requirement:
Each user needs to receive different notifications, based on rules defined in the database.

Say my service detects a change in the database (a new product of type ‘wine’ was inserted to the database) – it now needs to notify the clients. But not all clients need to be notified about this. Only clients that have requested to be updated about wine should be notified.

How do I do this ?

Once the client connects and is validated using the UserNamePasswordValidator – do I have some sort of ‘ClientID’ attached to that client ?

I know that I should not store a local list of ‘client endpoint+client ID’ in my service, because that means I have to use a Singleton service, right ?

So how can I store for each client that connects to the service – the ID of that client ?

I need to know the ID of each client, so that when an event in the database occurs – I can loop over every connected client – check for each one if he requested to be informed about that event – and if so – notify him about that event.

Hope my question is understood …

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1 Answer

  1. Editorial Team

    I think it would be difficult to achieve this in practise.

    A possible solution would involve maintaining many different lists of your service callback contract and expose the same number of subscribe operations. So your clients would call a subscribe operation for each of the events they are interested in and your service would then be able to call the clients callback contract once for each of the subscribed events.

    However you would have to know exactly what your clients want to subscribe to in advance because this information would be codified on the exposed service contract and would therefore be costly to change.

    How you would link this to rules defined in your database I don’t know.

    The other way of handling this is to move to a pubsub messaging platform like NServiceBus, but this means moving away from using WCF.

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