I have reported a bug on that we should make it Serializable.
There is a json converter for Url located in EPiServer.Cms.Shell.Json. If that might be helpful to you.
Are you using the XMLSerializer to serialize and then missing the Serilizable attribute on Url or are you doing it some other way?
Have you fixed it @Crowwman ? Would be nice to have MultipleProperty available for Epi 7 development!
I have been holding off on attempting to rework ElencySolutions.MultipleProperty to work with EPiServer 7 mainly due to some of the bugs I was coming across in the preview versions.
As EPiServer 7 was officially made available today I have started to make all of the necessary changes to make it compatable with EPiServer 7 but unfortunately I have come across one issue.
MultipleProperty serializes entities to strings and stores the xml in a property. Unfortunately the new EPiServer.Url class which is used as the underlying type for Page links, image links etc is not serializable. I guess this is just an oversight.
Would it be possible to make this object Serializable in future releases?