Build RESTful service with WCF - wcf

Question

I'm not new to web services or wcf but currently I'm stuck in a problem I couldn't find a solution for yet. I tried everything I've found searching stack overflow, but nothing solved the problem.
I'm trying to write a very small service using WCF that should return the result as XML, Json or CSV. For this I wrote the following code:
<ServiceContract()>
Public Interface IPortalExchangeService
<OperationContract()> _
<WebGet(BodyStyle:=WebMessageBodyStyle.Wrapped, ResponseFormat:=WebMessageFormat.Xml, UriTemplate:="belegungskalender/xml/{anbieter}/{subD}")> _
Function XMLData(ByVal anbieter As String, ByVal subD As String) As String
<OperationContract()> _
<WebGet(BodyStyle:=WebMessageBodyStyle.Wrapped, ResponseFormat:=WebMessageFormat.Json, UriTemplate:="belegungskalender/json/{anbieter}/{subD}")> _
Function JSONData(ByVal anbieter As String, ByVal subD As String) As String
<OperationContract()> _
<WebGet(UriTemplate:="belegungskalender/csv/{anbieter}/{subD}")> _
Function CSVData(anbieter As String, subD As String) As System.IO.Stream
End Interface
Now the class implementing the interface
Imports System.IO
Public Class CalendarExchangeService
Implements IPortalExchangeService
Public Sub New()
End Sub
Public Function XMLData(ByVal anbieter As String, ByVal subD As String) As String Implements IPortalExchangeService.XMLData
Return String.Format("You entered: {0}", subD)
End Function
Public Function JSONData(ByVal anbieter As String, ByVal subD As String) As String Implements IPortalExchangeService.JSONData
Return String.Format("You entered: {0}", subD)
End Function
Public Function CSVData(ByVal anbieter As String, ByVal subD As String) As Stream Implements IPortalExchangeService.CSVData
Dim ms As New MemoryStream
Dim enc As New UTF8Encoding
Dim arrBytData() As Byte = enc.GetBytes("Hallo;" + anbieter + ";hier;sind;die;Daten;von;" + subD)
ms.Write(arrBytData, 0, arrBytData.Length)
ms.Position = 0
WebOperationContext.Current.OutgoingResponse.ContentType = "text/csv"
Return ms
End Function
End Class
The web.config looks like this:
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<system.web>
<compilation debug="true" strict="false" explicit="true" targetFramework="4.0" />
</system.web>
<system.serviceModel>
<services>
<service name="PortalExchangeService" behaviorConfiguration="pesBehavior">
<endpoint address=""
binding="webHttpBinding"
bindingConfiguration=""
behaviorConfiguration="restfulBehavior"
contract="IPortalExchangeService">
</endpoint>
</service>
</services>
<behaviors>
<endpointBehaviors>
<behavior name="restfulBehavior">
<webHttp />
</behavior>
</endpointBehaviors>
<serviceBehaviors>
<behavior name="pesBehavior">
<serviceMetadata httpGetEnabled="true" />
<serviceDebug includeExceptionDetailInFaults="true" />
</behavior>
<behavior>
<serviceMetadata httpGetEnabled="true" />
<serviceDebug includeExceptionDetailInFaults="true" />
</behavior>
</serviceBehaviors>
</behaviors>
<serviceHostingEnvironment multipleSiteBindingsEnabled="true" />
</system.serviceModel>
<system.webServer>
<modules runAllManagedModulesForAllRequests="true"/>
</system.webServer>
</configuration>
And last not least the Client Code:
Dim url As String = "http://localhost:24642/PortalExchangeService.svc/belegungskalender/xml/testanbieter/subDomain"
Dim myRequest As HttpWebRequest = CType(WebRequest.Create(url), HttpWebRequest)
myRequest.ContentType = "application/xml"
myRequest.Method = "GET"
Dim myResponse As HttpWebResponse
myResponse = CType(myRequest.GetResponse(), HttpWebResponse)
Dim streamResponse As Stream = myResponse.GetResponseStream()
Dim streamRead As StreamReader = New StreamReader(streamResponse)
Dim readBuffer(255) As Char
Dim count As Integer = streamRead.Read(readBuffer, 0, 256)
Dim result As String = String.Empty
Do While (count > 0)
Dim resultData As String = New String(readBuffer, 0, count)
count = streamRead.Read(readBuffer, 0, 256)
result &= resultData
Loop
streamRead.Close()
streamResponse.Close()
myResponse.Close()
This all looked good to me, but running the client code I'm getting a "400 Bad Request" with no further information in the line
"myResponse = CType(myRequest.GetResponse(), HttpWebResponse)"
Testing the Service with WCF-Client Tool works fine, but calling with HTTP GET never.
Any ideas what I'm doing wrong?
Thank in advance for your tips!!
Best regards,
Henner