jQuery AJAX post to my ASP.NET webservice with JSON.stringify

I'm trying to trigger a jQuery AJAX post to my ASP.NET webservice. However, even though the subscribeToSearch method is executed, when I access the strSubscriber.email variable in that method it's empty. Why?

These are the varaible values I'm logging before they get posted:

email: [email protected]
objecttype: 15
provinceid: 7
city: "test"
distance: 0
minprice: 0
maxprice: 0
frequency: 0
rooms: 0
surface: 0

Here's the AJAX call:

   $.ajax({
        type: "POST",
        url: '/api/subscribetosearch',
        async: true,
        data: JSON.stringify({
            str: {
                'objecttype': objecttype,
                'email': email,
                'provinceid': provinceid,
                'city': city,
                'distance': distance,
                'minprice': minprice,
                'maxprice': maxprice,
                'frequency': frequency,
                'rooms': rooms,
                'surface': surface
            }
        }),
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        error: function () {
        },
        success: function (msg) {


        }
    }); 

The webmethod signatures:

Ihouse.vb

    <OperationContract()>
    <Web.WebInvoke(Method:="POST", ResponseFormat:=Web.WebMessageFormat.Json, BodyStyle:=Web.WebMessageBodyStyle.WrappedRequest,
UriTemplate:="subscribetosearch")>
    Function subscribeToSearch(ByVal str As GlobalFunctions.SearchSubscriber) As Stream 

house.svc.vb

Public Function subscribeToSearch(ByVal strSubscriber As GlobalFunctions.SearchSubscriber) As Stream Implements Ihouse.subscribeToSearch
    LogError("subscribeToSearch hit")
    LogError("subscribeToSearch email: " + strSubscriber.email)
End Function

I checked out the headers in Google Chrome dev console and this is the request payload:

Here's the SearchSubscriber class.

Public Class GlobalFunctions

    <Runtime.Serialization.DataContract>
    Public Class SearchSubscriber
        <Runtime.Serialization.DataMember>
        Private _objecttype As Integer
        Public Property objecttype() As Integer
            Get
                Return _objecttype
            End Get
            Set(ByVal value As Integer)
                _objecttype = value
            End Set
        End Property

        Private _email As String
        Public Property email() As String
            Get
                Return _email
            End Get
            Set(ByVal value As String)
                _email = value
            End Set
        End Property

        Private _provinceid As Integer
        Public Property provinceid() As Integer
            Get
                Return _provinceid
            End Get
            Set(ByVal value As Integer)
                _provinceid = value
            End Set
        End Property

        Private _city As String
        Public Property city() As String
            Get
                Return _city
            End Get
            Set(ByVal value As String)
                _city = value
            End Set
        End Property

        Private _distance As Integer
        Public Property distance() As Integer
            Get
                Return _distance
            End Get
            Set(ByVal value As Integer)
                _distance = value
            End Set
        End Property

        Private _minprice As Integer
        Public Property minprice() As Integer
            Get
                Return _minprice
            End Get
            Set(ByVal value As Integer)
                _minprice = value
            End Set
        End Property

        Private _maxprice As Integer
        Public Property maxprice() As Integer
            Get
                Return _maxprice
            End Get
            Set(ByVal value As Integer)
                _maxprice = value
            End Set
        End Property

        Private _frequency As Integer
        Public Property frequency() As Integer
            Get
                Return _frequency
            End Get
            Set(ByVal value As Integer)
                _frequency = value
            End Set
        End Property

        Private _rooms As Integer
        Public Property rooms() As Integer
            Get
                Return _rooms
            End Get
            Set(ByVal value As Integer)
                _rooms = value
            End Set
        End Property

        Private _surface As Integer
        Public Property surface() As Integer
            Get
                Return _surface
            End Get
            Set(ByVal value As Integer)
                _surface = value
            End Set
        End Property

    End Class
End Class   

UPDATE 1

Followed suggestions by @Nkosi so now I have this:

//construct the object to be posted.
var searchSubscriber = {
    objecttype: objecttype,
    email: email,
    provinceid: provinceid,
    city: city,
    distance: distance,
    minprice: minprice,
    maxprice: maxprice,
    frequency: frequency,
    rooms: rooms,
    surface: surface
};

$.ajax({
    type: "POST",
    url: '/api/subscribetosearch',
    async: true,
    data: JSON.stringify(searchSubscriber),
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    error: function () {
    },
    success: function (msg) {

    }
}); 

The request payload is now:

The following method on the server is hit, but the strSubscriber object is nothing...

Public Function subscribeToSearch(ByVal strSubscriber As GlobalFunctions.SearchSubscriber) As Stream Implements Ihouse.subscribeToSearch
    LogError("subscribeToSearch HIT")  <---- this line gets executed

    If strSubscriber Is Nothing Then
        LogError("subscribeToSearch strSubscriber IS NOTHING")  <---- this line gets executed
    Else
        LogError("subscribeToSearch strSubscriber IS SOMETHING")
    End If              

End Function