WCF and Input Parameter Order in SOAP Envelope

问题:

I'm getting an Object reference not set to an instance of object error in my WCF web service which uses webHttpBinding (soap 1.1) I have noticed that if you have the input parameters in a certain order the error does not get raised.

i.e.

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:not="http://schemas.globalfoundries.com/NotificationService">
   <soapenv:Header/>
   <soapenv:Body>
      <not:NotifyWorkflowItemUpdate>
         <not:userIDs>testUserID</not:userIDs>
         <not:taskID>testTaskID</not:taskID>
         <not:taskType>testTaskType</not:taskType>
         <not:status>testStatus</not:status>
         <not:appID>testAppID</not:appID>
         <not:message>testMessage</not:message>
      </not:NotifyWorkflowItemUpdate>
   </soapenv:Body>
</soapenv:Envelope>

However if I change the order of the input parameters in the request template I get the aforementioned error. i.e. (note message and userIDs parameters are switched)

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:not="http://schemas.globalfoundries.com/NotificationService">
   <soapenv:Header/>
   <soapenv:Body>
      <not:NotifyWorkflowItemUpdate>
     <not:message>testMessage</not:message>
         <not:taskID>testTaskID</not:taskID>
         <not:taskType>testTaskType</not:taskType>
         <not:status>testStatus</not:status>
         <not:appID>testAppID</not:appID>
         <not:userIDs>testUserID</not:userIDs>
      </not:NotifyWorkflowItemUpdate>
   </soapenv:Body>
</soapenv:Envelope>

Why is this happening? Are request parameters mapped to the .Net method parameters via the order and not by the names? Is there an attribute that I have to specify on the service contract to make named parameter mapping possible?

回答1:

You need to use XmlSerializerFormat class in your WCF service interface.

[ServiceContract, XmlSerializerFormat]
public interface IGoodMessageService
{
    ...
}

Problem and solution is explained in this link: http://neimke.blogspot.com.tr/2012/03/serialization-ordering-causes-problems.html

回答2:

The XML schema of your SOAP message specifies the order. In XML order of element matters and WCF is validating the XML against the schema.