WCF Webservice always returning null

Question

I am consuming a SOAP webservice from our ticket system OTRS. So the Webservice is not really under my control. The request works just fine, but i am never getting an answer in my Code. The answer is always null. (var response = client.SessionCreate(session);) The strange thing is, that wireshark and the webservice console of that ticket system are saying that i should receive a valid answer. Since i am very new to this webservice stuff so i have absolutely no idea where to start in this case. So here is a description of that i did. Any suggestion is really appreciated.

First i created a normal C# project and added the WSDL file which can be found only on the GitHub site website of the OTRS project. I added it as a Service Reference and than added my C# code which looks like this.

// For Debug System.Net.ServicePointManager.Expect100Continue = false; Thread.CurrentThread.CurrentUICulture = new CultureInfo("en-us");

try
{
    OTRS.OTRS_Error err = new OTRS.OTRS_Error();
    OTRS.GenericTicketConnector_PortTypeClient client = new OTRS.GenericTicketConnector_PortTypeClient("GenericTicketConnector_Port");

    OTRS.SessionCreate session = new OTRS.SessionCreate();
    session.Item = "someUserNameGoesHere";
    session.ItemElementName = OTRS.ItemChoiceType8.UserLogin;
    session.Password = "SomePasswordGoesHere";

    var response = client.SessionCreate(session);

    Console.WriteLine(response.SessionID);
    Console.WriteLine(response.Error);
}
catch (Exception exep) 
{
    Console.WriteLine(exep.Message);
    Console.WriteLine(exep.InnerException);
}
finally 
{
    Console.ReadLine();
}

Incoming message at serverside

<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:a="http://www.w3.org/2005/08/addressing">
<s:Header>
    <a:Action s:mustUnderstand="1">http://www.otrs.org/TicketConnector/SessionCreate</a:Action>
    <a:MessageID>urn:uuid:14750529-3de2-4618-8db4-8ac18b681c18</a:MessageID>
    <a:ReplyTo>
        <a:Address>http://www.w3.org/2005/08/addressing/anonymous</a:Address>
    </a:ReplyTo>
    <a:To s:mustUnderstand="1">http://SomeServer/otrs/nph-genericinterface.pl/Webservice/GenericTicketConnector</a:To>
</s:Header>
<s:Body xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <SessionCreate xmlns="http://www.otrs.org/TicketConnector/">
        <UserLogin xmlns="">someUserName</UserLogin>
        <Password xmlns="">somePassword</Password>
    </SessionCreate>
</s:Body>

Outgoing message at serverside

<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope soap:encodingStyle="http://www.w3.org/2003/05/soap-encoding" 
xmlns:soap="http://www.w3.org/2003/05/soap-envelope" 
xmlns:soapenc="http://www.w3.org/2003/05/soap-encoding" 
xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <soap:Body>
        <SessionCreateResponse xmlns="http://www.otrs.org/TicketConnector/">
            <SessionID>SomeSessionID</SessionID>
        </SessionCreateResponse>
    </soap:Body>
</soap:Envelope>

Wireshark HTTP/XML package going from the server to my client

<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope soap:encodingStyle="http://www.w3.org/2003/05/soap-encoding" 
xmlns:soap="http://www.w3.org/2003/05/soap-envelope" 
xmlns:soapenc="http://www.w3.org/2003/05/soap-encoding" 
xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <soap:Body>
        <SessionCreateResponse xmlns="http://www.otrs.org/TicketConnector/">
            <SessionID>SomeSessionID</SessionID>
        </SessionCreateResponse>
    </soap:Body>
</soap:Envelope>

Refernce.cs https://gist.github.com/HansVader/1ba3847d918ee15ef16703c8ada6c9bf

WSDL https://gist.github.com/HansVader/dd849e49f4a1584397cd21b0e430b301

I currently only need the SessionnCreate and TicketUpdate function. The other operations are irrelevant at this point in time. Please let me know if you need any other informations.

Update:

Here are the traces from the trace tool like yildizm85 suggested in the comments:

I think it is also worth noting that i created the refernce.cs by myself with the svcutil tool because i had a problem with the IsWrapped. Have a look at this question and answer: XmlSerializer attribute not valid in Web Service using WCF

Answer 1

The WSDL does not define elementFormDefault:

<xsd:schema targetNamespace="http://www.otrs.org/TicketConnector/" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> 

Since unqualified is default, this causes every property to be decorated with Form=System.Xml.Schema.XmlSchemaForm.Unqualified in the generated reference file.

But, since there is a default namespace specified for each complex object, the XML serializer will not process the unqualified properties.

The solution

Change the schema element to:

<xsd:schema targetNamespace="http://www.otrs.org/TicketConnector/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">

Also, for some of the properties, the order is wrong, so they need to be changed to (for example TickerCreateResponse):

<xsd:element name="TicketCreateResponse">
    <xsd:complexType>
        <xsd:sequence>
            <xsd:element maxOccurs="1" minOccurs="1" name="ArticleID" type="xsd:positiveInteger"/>
            <xsd:element maxOccurs="1" minOccurs="1" name="TicketID" type="xsd:positiveInteger"/>
            <xsd:element minOccurs="1" name="TicketNumber" type="xsd:string"/>
            <xsd:element maxOccurs="1" minOccurs="0" name="Error" type="tns:OTRS_Error"/>
        </xsd:sequence>
    </xsd:complexType>
</xsd:element>

After these changes, create the proxy using svcutil:

svcutil.exe /serializer:XmlSerializer GenericTicketConnectorSOAP.wsdl /o:OtrsConnector.cs /wrapped /n:*,otrs

And using the config:

<system.serviceModel>
<bindings>
  <customBinding>
    <binding name="GenericTicketConnector_Binding">
      <textMessageEncoding messageVersion="Soap12" writeEncoding="utf-8" />
      <httpTransport />
    </binding>
  </customBinding>
</bindings>
<client>
  <endpoint address="http://localhost/otrs/nph-genericinterface.pl/Webservice/GenericTicketConnector"
    binding="customBinding" bindingConfiguration="GenericTicketConnector_Binding"
    contract="otrs.GenericTicketConnector_PortType" name="GenericTicketConnector_Port" />
</client>
</system.serviceModel>

It should work after that, at least it did for me.

Hope it works for you as well!