I have a web service, which takes lot of time to execute. I am planning to delegate the processing task to a background thread & return the acknowledgement response to the user immediately.
In this case I was worried about the life-time of the background thread.
Will background thread complete the delegated task, before main method/thread finishes execution?
You should call your service asynchronously.
Refer to How to: Call WCF Service Operations Asynchronously for more details.