SOAP error. Need urgent help.

[Indrasish N Basuroychowdhury]

I am getting a SOAP error after sending the following SOAP envelope. Need help desparately. Any help will be appreciated.

<SOAP-ENV:Body>
<ReturnService xmlns="http://localhost/FirstTry/WebServices/">
<ah><Username>User</Username><Password>Pass</Password></ah>
</ReturnService>
</SOAP-ENV:Body>

SOAP error is following:
Env:[Attributes={ xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance" xmlns:xsd="http://www.w3.org/1999/XMLSchema"}] [Header=null] [Body=[Attributes={}] [BodyEntries=]] [EnvelopeEntries=]
SOAP Message:<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Body>
    <soap:Fault>
      <faultcode>soap:Server</faultcode>
      <faultstring>System.Web.Services.Protocols.SoapException: Server was unable to process request. ---&gt; System.Exception: There was an error generating the XML document. ---&gt; System.Exception: The type fanniemae.TestArray.ReturnObj was not expected. Use the XmlInclude or SoapInclude attribute to specify types that are not known statically.
   at System.Xml.Serialization.XmlSerializationWriter.WriteTypedPrimitive(String name, String ns, Object o, Boolean xsiType)
   at n2499d7d93ffa468fbd8861780677ee41.XmlSerializationWriter1.Write2_Object(String n, String ns, Object o, Boolean isNullable, Boolean needType)
   at n2499d7d93ffa468fbd8861780677ee41.XmlSerializationWriter1.Write4_ReturnServiceResponse(Object[] p)
   at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o, XmlSerializerNamespaces namespaces)
   at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o)
   at System.Web.Services.Protocols.SoapServerProtocol.WriteReturns(Object[] returnValues, Stream outputStream)
   at System.Web.Services.Protocols.WebServiceHandler.WriteReturns(Object[] returnValues)
   at System.Web.Services.Protocols.WebServiceHandler.Invoke()
   at System.Web.Services.Protocols.WebServiceHandler.CoreProcessRequest()</faultstring>
      <detail />
    </soap:Fault>
  </soap:Body>
</soap:Envelope>

The http requst and response is following:
The following is a sample SOAP request and response. The placeholders shown need to be replaced with actual values.

POST /FirstTry/WebServices/Array/TestArray.asmx HTTP/1.1
Host: localhost
Content-Type: text/xml; charset=utf-8
Content-Length: length
SOAPAction: "http://localhost/FirstTry/WebServices/ReturnService"

<?xml version="1.0" encoding="utf-8"?>
<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:Body>
    <ReturnService xmlns="http://localhost/FirstTry/WebServices/">
      <ao>
        <ArrayObj>
          <Username>string</Username>
          <Password>string</Password>
        </ArrayObj>
        <ArrayObj>
          <Username>string</Username>
          <Password>string</Password>
        </ArrayObj>
      </ao>
    </ReturnService>
  </soap:Body>
</soap:Envelope>
HTTP/1.1 200 OK
Content-Type: text/xml; charset=utf-8
Content-Length: length

<?xml version="1.0" encoding="utf-8"?>
<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:Body>
    <ReturnServiceResponse xmlns="http://localhost/FirstTry/WebServices/">
      <ReturnServiceResult>
        <Object />
        <Object />
      </ReturnServiceResult>
    </ReturnServiceResponse>
  </soap:Body>
</soap:Envelope>
 

Thanks,

Indrasish.