The information in this post is based on Dynamics AX 2012 R3. It may or may not be valid for other versions.
I recently encountered the somewhat cryptic error message “No metadata class defined for data contract object” when trying to start a SysOperation controller class.
After a bit of investigation, it turns out that the cause of this was that I forgot to decorate the ClassDeclaration of the data contract class with the [DataContractAttribute] attribute.
It seems there are a couple of other possible causes, but the above is the by far most likely one. Strange that I haven’t encountered it before, but I guess I’ve never forgotten that attribute before, then 😉
Hereby noted for future reference 🙂