Why would a WebService return nulls when the actual service returns data?

I have a webservice (out of my control) that I have to talk to. I also have a packet-sniffer on the line, and the developers of the webservice aren't lying. I see data in the correct fields.

They are actually sending back all of the data that I requested. But the web-service code that is auto-generated from the WSDL file is giving me "null" as a value.

UPDATE: For clarification, the object returned is NOT null. The elements within the object are null. I don't know if that will help anyone or not. I'm totally stumped.

I used their WSDL file to generate my Web Reference. I checked my data types with the datatypes that the WSDL file has declared. And I used the code as listed below to perform the calls:

DT_MaterialMaster_LookupRequest req = new DT_MaterialMaster_LookupRequest();
req.MaterialNumber = "101*";
req.DocumentNo = "";
req.Description = "Pipe*";
req.Plant = "0000";

MI_MaterialMaster_Lookup_OBService srv = new MI_MaterialMaster_Lookup_OBService();

DT_MaterialMaster_Response resp = 
    srv.MI_MaterialMaster_Lookup_OB(new DT_MaterialMaster_LookupRequest[] { req });


// Note that the response here is ALWAYS null!!
Console.WriteLine(resp.Status);

The resp object is an actual object. It was generated properly. However, the Status and MaterialData fields are always null.

When I call the web service, I've placed a packet-sniffer on the line, and I can see that I've sent the following (linebreaks and indentions for my own sanity):

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" 
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<soap:Body>
    <MT_MaterialMaster_Lookup 
        xmlns="http://MyCompany.com/SomeCompany/mm/MaterialMasterSearch">
        <Request xmlns="">
            <MaterialNumber>101*</MaterialNumber>
            <Description>Pipe*</Description>
            <DocumentNo />
            <Plant>0000</Plant>
        </Request>
    </MT_MaterialMaster_Lookup>
</soap:Body>
</soap:Envelope>

The response that they send back SEEMS to be a valid response (linebreaks and indentions for my own sanity):

<SOAP:Envelope xmlns:SOAP='http://schemas.xmlsoap.org/soap/envelope/'>
<SOAP:Header />
    <SOAP:Body>
        <n0:MT_MaterialMaster_Response
           xmlns:n0='http://MyCompany.com/SomeCompany/mm/MaterialMasterSearch'
           xmlns:prx='urn:SomeCompany.com:proxy:BRD:/1SAI/TAS4FE14A2DE960D61219AE:701:2009/02/10'>
        <Response>
            <Status>No Rows Found</Status>
            <MaterialData />
        </Response>
    </n0:MT_MaterialMaster_Response>
</SOAP:Body>
</SOAP:Envelope>

The status shows that it actually received data... but the resp.Status and resp.MaterialData fields are always null. What have I done wrong?

UPDATE: The WSDL file is defined as:

<?xml version="1.0" encoding="utf-8"?>
<wsdl:definitions xmlns:p1="http://MyCompany.com/SomeCompany/mm/MaterialMasterSearch" name="MI_MaterialMaster_Lookup_OB" targetNamespace="http://MyCompany.com/SomeCompany/mm/MaterialMasterSearch" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/">
  <wsdl:types>
    <xsd:schema xmlns="http://MyCompany.com/SomeCompany/mm/MaterialMasterSearch" 
        targetNamespace="http://MyCompany.com/SomeCompany/mm/MaterialMasterSearch" 
        xmlns:xsd="http://www.w3.org/2001/XMLSchema">
      <xsd:element name="MT_MaterialMaster_Response" type="p1:DT_MaterialMaster_Response" />
      <xsd:element name="MT_MaterialMaster_Lookup" type="p1:DT_MaterialMaster_Lookup" />
      <xsd:complexType name="DT_MaterialMaster_Response">
    <xsd:sequence>
      <xsd:element name="Status" type="xsd:string">
        <xsd:annotation>
          <xsd:appinfo source="http://SomeCompany.com/xi/TextID">d48d03b040af11df99e300145eccb24e</xsd:appinfo>
        </xsd:annotation>
      </xsd:element>
      <xsd:element maxOccurs="unbounded" name="MaterialData">
        <xsd:annotation>
          <xsd:appinfo source="http://SomeCompany.com/xi/TextID">64908aa040a511df843700145eccb24e</xsd:appinfo>
        </xsd:annotation>
        <xsd:complexType>
          <xsd:sequence>
        <xsd:element name="MaterialNumber" type="xsd:string">
          <xsd:annotation>
            <xsd:appinfo source="http://SomeCompany.com/xi/TextID">64908aa140a511df848500145eccb24e</xsd:appinfo>
          </xsd:annotation>
        </xsd:element>
        <xsd:element minOccurs="0" name="Description" type="xsd:string">
          <xsd:annotation>
            <xsd:appinfo source="http://SomeCompany.com/xi/TextID">64908aa240a511df95bf00145eccb24e</xsd:appinfo>
          </xsd:annotation>
        </xsd:element>
        <xsd:element minOccurs="0" name="DocumentNo" type="xsd:string">
          <xsd:annotation>
            <xsd:appinfo source="http://SomeCompany.com/xi/TextID">64908aa340a511dfb23700145eccb24e</xsd:appinfo>
          </xsd:annotation>
        </xsd:element>
        <xsd:element minOccurs="0" name="UOM" type="xsd:string">
          <xsd:annotation>
            <xsd:appinfo source="http://SomeCompany.com/xi/TextID">3b5f14c040a611df9fbe00145eccb24e</xsd:appinfo>
          </xsd:annotation>
        </xsd:element>
        <xsd:element minOccurs="0" name="Hierarchy" type="xsd:string">
          <xsd:annotation>
            <xsd:appinfo source="http://SomeCompany.com/xi/TextID">64908aa440a511dfc65b00145eccb24e</xsd:appinfo>
          </xsd:annotation>
        </xsd:element>
        <xsd:element minOccurs="0" name="Plant" type="xsd:string">
          <xsd:annotation>
            <xsd:appinfo source="http://SomeCompany.com/xi/TextID">d48d03b140af11dfb78e00145eccb24e</xsd:appinfo>
          </xsd:annotation>
        </xsd:element>
        <xsd:element minOccurs="0" name="Procurement" type="xsd:string">
          <xsd:annotation>
            <xsd:appinfo source="http://SomeCompany.com/xi/TextID">d48d03b240af11dfb87b00145eccb24e</xsd:appinfo>
          </xsd:annotation>
        </xsd:element>
          </xsd:sequence>
        </xsd:complexType>
      </xsd:element>
    </xsd:sequence>
      </xsd:complexType>
      <xsd:complexType name="DT_MaterialMaster_Lookup">
    <xsd:sequence>
      <xsd:element maxOccurs="unbounded" name="Request">
        <xsd:annotation>
          <xsd:appinfo source="http://SomeCompany.com/xi/TextID">64908aa040a511df843700145eccb24e</xsd:appinfo>
        </xsd:annotation>
        <xsd:complexType>
          <xsd:sequence>
        <xsd:element minOccurs="0" name="MaterialN开发者_如何学Cumber" type="xsd:string">
          <xsd:annotation>
            <xsd:appinfo source="http://SomeCompany.com/xi/TextID">64908aa140a511df848500145eccb24e</xsd:appinfo>
          </xsd:annotation>
        </xsd:element>
        <xsd:element minOccurs="0" name="Description" type="xsd:string">
          <xsd:annotation>
            <xsd:appinfo source="http://SomeCompany.com/xi/TextID">64908aa240a511df95bf00145eccb24e</xsd:appinfo>
          </xsd:annotation>
        </xsd:element>
        <xsd:element minOccurs="0" name="DocumentNo" type="xsd:string">
          <xsd:annotation>
            <xsd:appinfo source="http://SomeCompany.com/xi/TextID">64908aa340a511dfb23700145eccb24e</xsd:appinfo>
          </xsd:annotation>
        </xsd:element>
        <xsd:element minOccurs="0" name="Plant" type="xsd:string">
          <xsd:annotation>
            <xsd:appinfo source="http://SomeCompany.com/xi/TextID">64908aa440a511dfc65b00145eccb24e</xsd:appinfo>
          </xsd:annotation>
        </xsd:element>
          </xsd:sequence>
        </xsd:complexType>
      </xsd:element>
    </xsd:sequence>
      </xsd:complexType>
    </xsd:schema>
  </wsdl:types>
  <wsdl:message name="MT_MaterialMaster_Lookup">
    <wsdl:part name="MT_MaterialMaster_Lookup" element="p1:MT_MaterialMaster_Lookup" />
  </wsdl:message>
  <wsdl:message name="MT_MaterialMaster_Response">
    <wsdl:part name="MT_MaterialMaster_Response" element="p1:MT_MaterialMaster_Response" />
  </wsdl:message>
  <wsdl:portType name="MI_MaterialMaster_Lookup_OB">
    <wsdl:operation name="MI_MaterialMaster_Lookup_OB">
      <wsdl:input message="p1:MT_MaterialMaster_Lookup" />
      <wsdl:output message="p1:MT_MaterialMaster_Response" />
    </wsdl:operation>
  </wsdl:portType>
  <wsdl:binding name="MI_MaterialMaster_Lookup_OBBinding" type="p1:MI_MaterialMaster_Lookup_OB">
    <binding transport="http://schemas.xmlsoap.org/soap/http" xmlns="http://schemas.xmlsoap.org/wsdl/soap/" />
    <wsdl:operation name="MI_MaterialMaster_Lookup_OB">
      <operation soapAction="http://SomeCompany.com/xi/WebService/soap1.1" xmlns="http://schemas.xmlsoap.org/wsdl/soap/" />
      <wsdl:input>
    <body use="literal" xmlns="http://schemas.xmlsoap.org/wsdl/soap/" />
      </wsdl:input>
      <wsdl:output>
    <body use="literal" xmlns="http://schemas.xmlsoap.org/wsdl/soap/" />
      </wsdl:output>
    </wsdl:operation>
  </wsdl:binding>
  <wsdl:service name="MI_MaterialMaster_Lookup_OBService">
    <wsdl:port name="MI_MaterialMaster_Lookup_OBPort" binding="p1:MI_MaterialMaster_Lookup_OBBinding">
      <address location="http://bxdwas.MyCompany.com/XISOAPAdapter/MessageServlet?channel=:SOAP_SND_Material_Lookup" xmlns="http://schemas.xmlsoap.org/wsdl/soap/" />
    </wsdl:port>
  </wsdl:service>
</wsdl:definitions>

You'd have to post the WSDL for me to be sure, but "Web Service Returns Null" almost always means there's a dispute about XML Namespaces - the service is sending you data in one namespace, and .NET is expecting a different namespace.

In this case, note that most of the response is in the default namespace, even though the wrapper element is in the http://MyCompany.com/SomeCompany/mm/MaterialMasterSearch namespace.

Make sure your service references are up to date. This happens to us when the service WSDL changed but the references were not updated.