WCF Disable Deserialization Order Sensitivity

Question

I have a recurring problem when passing Serialized objects between non-.NET Clients, and .NET WCF Services.

When WCF Deserializes objects, it is strictly dependant

Answer 1

You can use the IsRequired property of the DataMember attribute to specify that the elements are required. In that way, instead of getting "mysterious" null value, you'll get a more explicit error message indicating that a required element is missing.

[DataContract]
public class Foo 
{ 
  [DataMember(IsRequired=true, Order=1)]
  public int ID { get; set; } 

  [DataMember(IsRequired=true, Order=2)]
  public int Bar { get; set; } 
}

What's happening in your case is:

• The DataContract expects Bar and ID elements in that order (alphabetic because you haven't specified an explicit order).

• It encounters an ID element without a preceding Bar element. Since Bar is not required, it simply ignores it.

• The ID element following Bar is ignored because it is in the wrong position.

Having said that, setting IsRequired to true will only help in version 1 of your contract. Elements added in subsequent versions will normally have IsRequired set to false. MSDN has an article on data contract versioning.