Windows Phone 8 Unsupported API cannot be used by a background agent - dll

Question

I have built a Windows Phone 8 app which compiles and runs without any problems. However, when I run the built-in VS Store Test Kit, it brings back LOTS of errors under XAP package requirements, formatted as such:
[ERROR]: Unsupported API cannot be used by a background agent.
Assembly Microsoft.Phone.Controls.Toolkit.dll was trying to use
Microsoft.Phone.Shell.ApplicationBarIconButton.
I'm getting errors for my project dll ([projectname].dll) and the Toolkit dll. It seems to be bringing back everything, even references I'm not using (such as add_OrientationChanged).
Now I've had a look through the Unsupported APIs listed by Microsoft, and I'm not using any of them. At the bottom of the page is a list of "noteworthy APIs", the one of which I;m using is HTTPWebRequest to connect to a web service. I'm assuming this is where the problem lies, as I use this throughout the app.
Here's an example of what I'm doing with HTTPWebRequest:
Public Sub LoadRequest()
Dim request As HttpWebRequest = CType(WebRequest.Create(_ServiceURL), HttpWebRequest)
request.ContentType = "text/xml;charset=utf-8"
request.Method = "POST"
request.Headers("SOAPAction") = "<web service address>"
Start the asynchronous operation.
Dim result As IAsyncResult = _
CType(request.BeginGetRequestStream(AddressOf GetRequestsStreamCallback, request), _
IAsyncResult)
End Sub
Public Sub GetRequestsStreamCallback(ByVal asyncResult As IAsyncResult)
Dim request As HttpWebRequest = CType(asyncResult.AsyncState, HttpWebRequest)
Dim soapBody As System.Xml.Linq.XDocument = System.Xml.Linq.XDocument.Parse( _
"<soap:Envelope xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:xsd='http://www.w3.org/2001/XMLSchema' " & _
"xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/'><soap:Header><[SOAP Header Here]></soap:Header>" & _
"<soap:Body><[SOAP Body Here]></soap:Body></soap:Envelope>")
'End the operation
Dim postStream As Stream = request.EndGetRequestStream(asyncResult)
'Convert the string into byte array.
Dim byteArray As Byte() = Encoding.UTF8.GetBytes(soapBody.ToString())
'Write to the stream.
postStream.Write(byteArray, 0, soapBody.ToString().Length)
postStream.Close()
Dispatcher.BeginInvoke(Sub()
Dim result As IAsyncResult = _
CType(request.BeginGetResponse(AddressOf GetRequestsResponseCallback, request), IAsyncResult)
End Sub)
End Sub
Public Sub GetRequestsResponseCallback(ByVal Result As IAsyncResult)
'Get the response
Dim request As HttpWebRequest = CType(Result.AsyncState, HttpWebRequest)
Dim response As HttpWebResponse = CType(request.EndGetResponse(Result), HttpWebResponse)
Dim streamResponse As Stream = response.GetResponseStream()
Dim streamRead As New StreamReader(streamResponse)
Dim responseString As String = streamRead.ReadToEnd()
streamResponse.Close()
streamRead.Close()
'Take action on the response
Dim Xml As XDocument = XDocument.Parse(responseString)
Dim ns As XNamespace = "<Service Address>"
etc...
End Sub
I then proceed to pull apart the XML response for the data I need for the app. Any ideas as to what the test kit isn't happy about here? I'm assuming that as it doesn't pass validation at this stage, it's likely to be rejected from the store.
Thanks in advance for any ideas.

Answer 1

The problem was an existing background agent I was unaware of (I took over the project from another developer). There was a reference in the WMAppManifest.xml file, which was apparently part of an early test using the Wallet, which is no longer required. Removing this reference fixed the problem.
<ExtendedTask Name="BackgroundTask">
<BackgroundServiceAgent Specifier="WalletAgent" Name="WalletAgent" Source="<ProjectName>" Type="<ProjectName>.WPWalletAgent" />
</ExtendedTask>