Can CallbackEventHandler send multiple responses to the client?

Question

I've implemented ICallbackEventHandler to handle data sent from the browser's javascript. (The user clicks something, causing eventArgument to be sent to the server. The server invokes a service to obtain regarding that value.) Everything works great so far, but I actually need to invoke three different services with the same eventArgument. Depending on when/if each service responds, its results need to be sent to the browser for it to augment the display. I'm thinking of creating a thread for each service request. When/if it responds, then I'd send those results to the browser too.

What would be a good way to accomplish this?

//ICallbackEventHandler implementation 
public void RaiseCallbackEvent(String eventArgument)
{
   returnValue = GetDataFromService1(eventArgument);
}

public String GetCallbackResult()
{
   return returnValue;
}

Answer 1

The easiest way to implement this would be to implement javascript in the browser that polls for results from each service, given that each may return at a different time.

Another option might be Reactive Extensions for .NET (Rx). Rx offers "push" notifications to a browser using Observable collections implemented in .NET and "emitted" to javascript.