Microsoft Exam 70-487 Topic 4 Question 1 Discussion

You are developing a WCF service that compares several data sources. The service takes a long time to complete.

The service must meet the following requirements:

The client must be able to continue processing while the service is running.

The service must initiate communication with the client application when processing is complete.

You need to choose a message pattern to meet the requirements.

Which message pattern should you choose?