add $format=json support in query URL
Now WCF data service supports getting json-formatted response by specifying Accept=application/json header in request only. However, It does not support $format=json as a query option, although it could be circumvented by copying code from http://code.msdn.microsoft.com/DataServicesJSONP and decorating service class with [JSONPSupportBehavior]. The lack of its support is a well-known issue. Hopefully it can be fixed soon and save people hassles of copying extra code and compiling and publishing.
Pratik Patel (MSFT) commented
This is now supported in the 5.1 release.
Mike OShea commented
Seemingly minor, but would have been nice to have bundled into 5. Why not make it even easier to adopt this implementation?
Jovan Popovic commented
Julie Lerman commented
a shame this didn't make it into WCF Data Services 5. :(