I've deployed several services that share some of their data contracts. When I build a client application that calls more than one of the services, each service contributes a copy of the data contract during proxy generation. This causes a compile error because the same type is defined multiple times. How do I resolve the conflict?

Assuming that you don't want to change the services, there are four obvious ways to fix the conflict. Three of the ways are mostly manual and one of the ways is mostly automatic.

1. Manual resolution: split up the client application into separate compile units so that each of the compile units references only one of the services. This method is the most invasive and tedious solution.
2. Manual resolution: edit the output of proxy generation to place each service proxy in its own namespace. This method requires very little work but makes writing the client application inconvenient because types need to be namespace qualified and passing objects between different services becomes harder.
3. Manual resolution: edit the output of proxy generation to remove extra copies of types. This method requires the most work every time you want to regenerate the proxies but gives you the most freedom for building the client application the way you want.
4. Automatic resolution: treat proxy generation as an incremental process and use svcutil /r to reference type assemblies generated by earlier processed services. This method is possible to fully automate but introduces complications into the proxy generation process. This method is the best long-term solution but requires infrastructure work that may be too much overhead for smaller projects.

Next time: Cleaning up Async