Your struct should also be decorated with a [DataContract]
+ Decorate it's members with a [DataMember]
:
[StructLayout(LayoutKind.Sequential)]
[DataContract]
public struct Invoice_Body_Item
{
[DataMember]
public string Item_Description;
[DataMember]
public decimal Item_Value;
}
Alternatively, you can use the [KnownTypeAttribute(typeof(Invoice_Body_Item))]