Invoking a WCF method that takes a List of objects

I have a WCF service that's consumed via an iPhone application. All other methods that accept string parameters or single objects are working fine, however when I invoke a method that takes a "List<CustomObjectClass> ssf".

I am passing an NSMutableArray of CustomObjectClass's to this method and I'm getting the following error:

Any ideas?

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"><s:Body><s:Fault><faultcode xmlns:a="http://schemas.microsoft.com/net/2005/12/windowscommunicationfoundation/dispatcher">a:DeserializationFailed</faultcode><faultstring xml:lang="en-AU">The formatter threw an exception while trying to deserialize the message: There was an error while trying to deserialize parameter http://tempuri.org/:ssf. The InnerException message was 'Error in line 2 position 6. Expecting state 'Element'.. Encountered 'Text'  with name '', namespace ''. '.  Please see InnerException for more details.</faultstring><detail><ExceptionDetail xmlns="http://schemas.datacontract.org/2004/07/System.ServiceModel" xmlns:i="http://www.w3.org/2001/XMLSchema-instance"><HelpLink i:nil="true"/><InnerException><HelpLink i:nil="true"/><InnerException i:nil="true"/><Message>Error in line 2 position 6. Expecting state 'Element'.. Encountered 'Text'  with name '', namespace ''. </Message><StackTrace>   at ReadArrayOfScanShareFriendFromXml(XmlReaderDelegator , XmlObjectSerializerReadContext , XmlDictionaryString , XmlDictionaryString , CollectionDataContract )&#xD;
   at System.Runtime.Serialization.CollectionDataContract.ReadXmlValue(XmlReaderDelegator xmlReader, XmlObjectSerializerReadContext context)&#xD;
   at System.Runtime.Serialization.XmlObjectSerializerReadContext.ReadDataContractValue(DataContract dataContract, XmlReaderDelegator reader)&#xD;
   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator reader, String name, String ns, Type declaredType, DataContract&amp; dataContract)&#xD;
   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator xmlReader, Type declaredType, DataContract dataContract, String name, String ns)&#xD;
   at System.Runtime.Serialization.DataContractSerializer.InternalReadObject(XmlReaderDelegator xmlReader, Boolean verifyObjectName, DataContractResolver dataContractResolver)&#xD;
   at System.Runtime.Serialization.XmlObjectSerializer.ReadObjectHandleExceptions(XmlReaderDelegator reader, Boolean verifyObjectName, DataContractResolver dataContractResolver)&#xD;
   at System.Runtime.Serialization.DataContractSerializer.ReadObject(XmlDictionaryReader reader, Boolean verifyObjectName)&#xD;
   at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.DeserializeParameterPart(XmlDictionaryReader reader, PartInfo part, Boolean isRequest)</StackTrace><Type>System.Runtime.Serialization.SerializationException</Type></InnerException><Message>The formatter threw an exception while trying to deserialize the message: There was an error while trying to deserialize parameter http://tempuri.org/:ssf. The InnerException message was 'Error in line 2 position 6. Expecting state 'Element'.. Encountered 'Text'  with name '', namespace ''. '.  Please see InnerException for more details.</Message><StackTrace>   at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.DeserializeParameterPart(XmlDictionaryReader reader, PartInfo part, Boolean isRequest)&#xD;
   at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.DeserializeParameter(XmlDictionaryReader reader, PartInfo part, Boolean isRequest)&#xD;
   at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.DeserializeParameters(XmlDictionaryReader reader, PartInfo[] parts, Object[] parameters, Boolean isRequest)&#xD;
   at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.DeserializeBody(XmlDictionaryReader reader, MessageVersion version, String action, MessageDescription messageDescription, Object[] parameters, Boolean isRequest)&#xD;
   at System.ServiceModel.Dispatcher.OperationFormatter.DeserializeBodyContents(Message message, Object[] parameters, Boolean isRequest)&#xD;
   at System.ServiceModel.Dispatcher.OperationFormatter.DeserializeRequest(Message message, Object[] parameters)&#xD;
   at System.ServiceModel.Dispatcher.DispatchOperationRuntime.DeserializeInputs(MessageRpc&amp; rpc)&#xD;
   at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc&amp; rpc)&#xD;
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc&amp; rpc)&#xD;
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage41(MessageRpc&amp; rpc)&#xD;
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage4(MessageRpc&amp; rpc)&#xD;
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage31(MessageRpc&amp; rpc)&#xD;
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage3(MessageRpc&amp; rpc)&#xD;
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage2(MessageRpc&amp; rpc)&#xD;
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage11(MessageRpc&amp; rpc)&#xD;
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage1(MessageRpc&amp; rpc)&#xD;
   at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)</StackTrace><Type>System.ServiceModel.Dispatcher.NetDispatcherFaultException</Type></ExceptionDetail></detail></s:Fault></s:Body></s:Envelope>

It looks like the SOAP message that was sent from iPhone application is not in format expected by the WCF service. If that's the case, you will probably have to take more control over serialization of NSMutableArray of CustomObjectClasses when passing the array to the method.

In order to check whether that is the issue, you could implement and configure WCF message inspector that would write the SOAP request message into a file and then review the file to check whether it looks like following SOAP message:

<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://tempuri.org/IService/SendData</a:Action>
        <a:MessageID>urn:uuid:8a582916-1b9a-47f8-8fb1-c9ff18420391</a:MessageID>
        <a:ReplyTo>
            <a:Address>http://www.w3.org/2005/08/addressing/anonymous</a:Address>
        </a:ReplyTo>
        <a:To s:mustUnderstand="1">net.tcp://localhost:13031/Service</a:To>
    </s:Header>
    <s:Body>
        <SendData xmlns="http://tempuri.org/">
            <ssf xmlns:b="http://schemas.datacontract.org/2004/07/Common"
                 xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
                <!-- Zero or more CustomObjectClass elements-->
                <b:CustomObjectClass>
                    <!-- Zero or more elements for CustomObjectClass properties -->
                </b:CustomObjectClass>
            </ssf>
        </SendData>
    </s:Body>
</s:Envelope>

Implement WCF message inspector:

Implement WCF message inspector(IDispatchMessageInspector).
Implement endpoint behavior (IEndpointBehavior).
Implement custom behavior extension element (BehaviorExtensionElement).

WCF message inspector:

public class FileOutputMessageInspector : IDispatchMessageInspector
{
    public object AfterReceiveRequest( ref Message request, IClientChannel channel,
        InstanceContext instanceContext )
    {
        string path = Path.Combine(
            AppDomain.CurrentDomain.SetupInformation.ApplicationBase,
            Guid.NewGuid().ToString() + ".xml"
        );
        File.WriteAllText( path, request.ToString() );
        return null;
    }

    public void BeforeSendReply( ref Message reply, object correlationState )
    { }
}

Endpoint behavior:

public class FileOutputBehavior : IEndpointBehavior
{
    public void AddBindingParameters( ServiceEndpoint endpoint,
        BindingParameterCollection bindingParameters )
    { }

    public void ApplyClientBehavior( ServiceEndpoint endpoint,
        ClientRuntime clientRuntime )
    {
        throw new ApplicationException( "Behavior is not supported on client side." );
    }

    public void ApplyDispatchBehavior( ServiceEndpoint endpoint,
        EndpointDispatcher endpointDispatcher )
    {
        FileOutputMessageInspector inspector = new FileOutputMessageInspector();
        endpointDispatcher.DispatchRuntime.MessageInspectors.Add( inspector );
    }

    public void Validate( ServiceEndpoint endpoint )
    { }
}

Behavior extension element:

public class FileOutputElement : BehaviorExtensionElement
{
    public override Type BehaviorType
    {
        get { return typeof( FileOutputBehavior ); }
    }

    protected override object CreateBehavior()
    {
        return new FileOutputBehavior();
    }
}

Configure WCF message inspector:

Declare new behavior extension (Make sure that the correct full type name is used in type attribute).
Use the declared behavior extension in an endpoint behavior.
Reference the endpoint behavior.

Use following configuration as reference:

<system.serviceModel>
    <services>
        <service name="Server.Service">
            <endpoint address=""
                      binding="netTcpBinding" bindingConfiguration="TCP"
                      contract="Common.IService"
                      behaviorConfiguration="RequestMessageToFile"/>
            <host>
                <baseAddresses>
                    <add baseAddress="net.tcp://localhost:13031/Service"/>
                </baseAddresses>
            </host>
        </service>
    </services>
    <bindings>
        <netTcpBinding>
            <binding name="TCP">
                <security mode="None"/>
            </binding>
        </netTcpBinding>
    </bindings>
    <behaviors>
        <endpointBehaviors>
            <behavior name="RequestMessageToFile">
                <requestFileOutput />
            </behavior>
        </endpointBehaviors>
    </behaviors>
    <extensions>
        <behaviorExtensions>
            <add name="requestFileOutput"
                 type="Common.FileOutputElement, Common"/>
        </behaviorExtensions>
    </extensions>
</system.serviceModel>