We are currently using the Silverlight API version 3.0 and whenever we try to initialize an ArcGISDynamicMapServiceLayer from a 10.4 server we are getting InvalidCastException Unable to cast object of type 'System.String' to type 'System.Collections.ICollection'.
I know the latest (and final) Silverlight API is version 3.3, but upgrading breaks a lot of our existing code, and before spending any time trying to fix our code to upgrade to version 3.3 I was wanting to know if anyone else is having the same problems when running version 3.3
I've seen that other people have had the same problem https://geonet.esri.com/thread/173642, but I don't know what API version they were using.
If this is a known issue for the Silverlight API 3.3, then we would rather just stick with our current API version and continue putting our focus on moving away from Silverlight entirely.