Custom (de)serializers can't be used across assemblies

[Alexejhero]

A custom serializer/deserializer (Read/Write extension method) in an assembly can only be used within that assembly, and does not work in other assemblies even if they have a reference to the one containing the methods.

TO REPRODUCE:

1. Make custom serializer and deserializer for type X in assembly A
2. Make rpc method with type X in assembly B
3. 🔥 even though B references A