WCF Datacontract, some fields do not deserialize

Problem:

I have a WCF service setup to be an endpoint for a call from an external system. The call is sending plain xml. I am testing the system by sending calls into the service from Fiddler using the RequestBuilder.

The issue is that all of my fields are being deserialized with the exception of two fields. price_retail and price_wholesale.

What am I missing? All of the other fields deserialize without an issue - the service responds. It is just these fields.

XML Message:

<widget_conclusion>
    <list_criteria_id>123</list_criteria_id>
    <list_type>consumer</list_type>
    <qty>500</qty>
    <price_retail>50.00</price_retail>
    <price_wholesale>40.00</price_wholesale>
    <session_id>123456789</session_id>
</widget_conclusion>

Service Method:

public string WidgetConclusion(ConclusionMessage message)
{
    var priceRetail = message.PriceRetail;
}

Message class:

[DataContract(Name = "widget_conclusion", Namespace = "")]
public class ConclusionMessage  
{
    [DataMember(Name = "list_criteria_id")]
    public int CriteriaId  { get; set;}
    [DataMember(Name = "list_type")]
    public string ListType { get; set; }
    [DataMember(Name = "qty")]
    public int ListQuantity { get; set; }
    [DataMember(Name = "price_retail")]
    public decimal PriceRetail { get; set; }
    [DataMember(Name = "price_wholesale")]
    public decimal PriceWholesale { get; set; }
    [DataMember(Name = "session_id")]
    public string SessionId { get; set; }
}

Fields are in the wrong order for your message. DataContracts default to Alphabetical ordering and not order of declaration; and expects XML elements to arrive in that order; Out of order elements are discarded usually.

Either fix your contract to specify the right order explicitly (using the Order property of the DataMemberAttribute) or make sure your client sends them in the right one.