serialization - WCF and .NET 5.0: Issue with byte array deserialization

Question

I'm trying to consume existing WCF services (basic binding) and I'm facing some issues related with the deserialization of the received message. Let me start by showing a snippet of the message:

<s:Body>
  <ObtemUtilizadoresResponse xmlns="http://xxx. pt/Mercados"><ObtemUtilizadoresResult xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
     <util>
       <Id>123</Id>
       <ver>AAAAAACL5j4=</ver>
       <im>-2</im>
       <n>User 123</n>
     </util>
   ....
</s:Body>

Initially, I've start by creating a new DTO for performing the deserialization which looks like this:

[DataContract(Namespace = "http://xxx.pt/Mercados", Name = "util")]
public class Utilizador {
    [field: DataMember(Name = "Id")]
    public int Id { get; set; }
    
    [field: DataMember(Name = "ver")]
    private byte[] Version { get; set; }
    
    [field: DataMember(Name = "n")]
    public string Nome { get; set; }
   
    [field: DataMember(Name = "im")]
    public int IdMercado { get; set; }
}

Even though the instance is created, it will only fill the Id and Version properties. If I remove the Version property, then the remaining properties are filled. In order to get all the properties filled, I had to move Version to a base class:

[DataContract(Namespace = "http://xxx. pt/Mercados", Name = "vb")]
public class Base {       
    [field: DataMember(Name = "ver")]
    private byte[] Version { get; set; }
}

[DataContract(Namespace = "http://xxx.pt/Mercados", Name = "util")]
public class Utilizador:Base {
... //removed Version property

Does anyone know why this is happening?

Thanks.

question from:https://stackoverflow.com/questions/65903958/wcf-and-net-5-0-issue-with-byte-array-deserialization

Answer 1

After some digging, it seems like there's an explanation for this behavior. When you use the DataContractSerializer, the default serialization order inside the type is alphabetical, and if you're using a class hierarchy, the order is top down. If there's a mismatch in the serialization order, the members will be initialized to their default values. That's why everything worked out fine when I introduced the base class (because the service uses a base class for the type being serialized).

So, if you want to flatten the hierarchy on the client side, you'll need to resort to the Order property of the DataMemberAttribute. You can apply the correct order position to each property (so that it mimics what's being serialized on the server) or you can "group" them by giving the same value to the properties that belong to the each level of the hierarchy (and rely on the the default alphabetical order for the properties that have the same order value - which, btw, is base on the Name property, if you're also setting it):

[DataContract(Namespace = "http://xxx.pt/Mercados", Name = "util")]
public class Utilizador {
    [field: DataMember(Name = "Id", Order = 1)]
    public int Id { get; set; }

    [field: DataMember(Name = "ver", Order = 1)]
    private byte[] Version { get; set; }

    [field: DataMember(Name = "n", Order = 2)]
    public string Nome { get; set; }

    [field: DataMember(Name = "im", Order = 2)]
    public int IdMercado { get; set; }
}