System.Runtime.Serialization.InvalidDataContractException: No set method for property

Question

As the error shows I don't have a setter for my property, but I don't want a setter, it should be readonly.

Answer 1

Edited: Make the setter internal.

This will still be settable within the assembly, but it is a nice trick that works well when used on data objects located within an assembly that is consumed by others, as those consuming assemblies will not be able to set the property, but the various serializers can.

Answer 2

Remember that WCF needs to create an instance of the object from its serialized representation (often XML) and if the property has no setter it cannot assign a value. Objects are not transferred between the client and the server but only serialized representations, so the object needs to be reconstructed at each end.