Serialize/deserialize objects - order of fields matters?

Question

Is it possible that DataContractSerializer wrongly deserializes object if fields are not in the "correct" (whatever that means) order? My classes that I serialize/deserialize do not have order attributes placed on fields/properties. Yet one of my fields always get deserialized as null although it has values, it actually contains a list of strings.

When I moved two XML elements in serialized file around to match the order in another sample XML (for which deserialization worked without problems) everything started to work.

This makes no sense to me but maybe someone knows better. ;)

Answer 1

To be eligible for correct serialization / serialization by the DataContractSerializer, all of the following must be true.

1. The class that must be serialized must have SerializableAttribute or DataContractAttribute set;
2. The properties and fields of the class that must be serialized require the DataMemberAttribute set;
3. The datatype of the serializable property or field must be serializable (i.e., have a public ctor and inherit ISerializable);
4. The class that must be serialized must implement IExtensibleDataObject;
5. Note: serializable fields can be either public or private.
6. Members must be in alphabetical order or you should use the Order-property of the DataMemberAttribute.

EDIT: This last point I only found out while typing your answer.

The order of the declaration does matter. If members are not in alphabetical order, they are skipped. Look up this answer at Stackoverflow for an example, perhaps it applies to your case.