Web API 2 XML Model Issues

Question

I've been thrown in the deep end a little and just can't figure out how to get the XML to fill out my model correctly.

I can get the two strings filling in fine, but as soon as I put in a property of a customer class then it just doesn't get the data.

My classes are:

Application Class:

Imports System
Imports System.Runtime.Serialization
Imports System.ServiceModel

<DataContract([Namespace]:="Application")>
Public Class AdvantageApplication

   <DataMember>
   Public Property Test1 As String
   <DataMember>
   Public Property Test2 As String
   <DataMember>
   Public Property Advantage As Advantage

   Public Sub New()

   End Sub

End Class

Advantage Class:

Imports System
Imports System.Runtime.Serialization

<DataContract(IsReference:=True)>
Public Class Advantage

<DataMember>
Public Property NumberOfApplicants As String

   Public Sub New()

   End Sub

End Class

My controller is:

Namespace Api
    Public Class SendApplicationController
        Inherits ApiController

        Public Function Post(<FromBody()> ByVal application As AdvantageApplication) As IHttpActionResult

        End Function
End Namespace

The XML I'm currently trying to receive is:

  <?xml version="1.0" ?> 
- <AdvantageApplication xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="Application">
      <Test1>Testing</Test1> 
      <Test2>1234</Test2> 
      <Advantage>
          <NumberOfApplicants>1</NumberOfApplicants> 
      </Advantage>
  </AdvantageApplication>

Test1 and Test2 is receiving data fine but I get nothing for the NumberOfApplicants and I've tried so much and just can't figure out what I'm doing wrong.

Thanks in advance for any help.