{"Type 'System.Object[]' cannot be added to list of known types since another
type 'System.Collections.ArrayList' with the same data contract name
'http://schemas.microsoft.com/2003/10/Serialization/Arrays:ArrayOfanyType' is
already present."}

Error deserializing my Response Object

I am getting an exception when deserializing on the client side.

{"Type 'System.Object[]' cannot be added to list of known types since
another type 'System.Collections.ArrayList' with the same data contract name
'http://schemas.microsoft.com/2003/10/Serialization/Arrays:ArrayOfanyType' is
already present."}

The service method looks like:

public ResponseEntity LoginUser(RequestEntity request)
       {
           _userFacade = new UserFacade(request.Agency);
           return _userFacade.LoginUser((string)request.RequestObjects[0],
(string)request.RequestObjects[1]);
       }

Where I am passing username and password as an array parameters on the
RequestEntity object.

The user Facade looks like:

public ResponseEntity LoginUser(string userID, string password)
       {
           var response = new ResponseEntity(String.Empty, false);
           try
           {
               var userBusinessController = new
UserBusinessController(AgencyName);
               User user = userBusinessController.LoginUser(userID,
password);
               response.ResponseObject = user;
               response.IsSuccess = true;
           }

           catch (Exception ex)
           {
               // ExceptionHandler.HandleException(ex,
My.Resources.FacadeResource.generic_policy);
               response = ProcessException(ex);
           }
           return response;
       }

The Response Object looks like:

[MessageContract]
   public class ResponseEntity
   {
       #region Private Members
       private Boolean _isSuccess;
       private object _responseObject;
       private string _message;
       #endregion

       #region Constructors

       public ResponseEntity()
       {
       }
       public ResponseEntity(string message, Boolean isSuccess)
       {
           _message = message;
           _isSuccess = isSuccess;
       }
       
       #endregion
       
       #region Properties

       [MessageBodyMember]
       public Boolean IsSuccess
       {
           get { return _isSuccess; }
           set { _isSuccess = value; }
       }
       [MessageBodyMember]
       public string Message
       {
           get { return _message; }
           set { _message = value; }
       }
       [MessageBodyMember]
       public object ResponseObject
       {
           get { return _responseObject; }
           set { _responseObject = value; }
       }
       #endregion

   }

Using the SVCtracerViewer I can see the message created on the server side
and looks like:

<MessageLogTraceRecord>
<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope"
xmlns:a="http://www.w3.org/2005/08/addressing"
xmlns:u="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
<s:Header>
<a:Action
s:mustUnderstand="1">http://www.cprops.com/IUserService/LoginUserResponse</a:Action>
<ActivityId CorrelationId="8696cbf9-9e55-4c2a-a4cc-ae339aff1e00"
xmlns="http://schemas.microsoft.com/2004/09/ServiceModel/Diagnostics">2fe8b8ac-9b53-487
6-9139-321d3645ab8f</ActivityId>
<a:RelatesTo>urn:uuid:997a9063-24c4-4b38-87ba-13b5bd79ba48</a:RelatesTo>
<o:Security s:mustUnderstand="1"
xmlns:o="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">
<u:Timestamp u:Id="_0">
<u:Created>2008-03-26T18:29:45.515Z</u:Created>
<u:Expires>2008-03-26T18:34:45.515Z</u:Expires>
</u:Timestamp>
</o:Security>
</s:Header>
<s:Body>
<ResponseEntity xmlns="http://www.cprops.com/">
<IsSuccess>true</IsSuccess>
<Message></Message>
<ResponseObject i:type="b:User"
xmlns:i="http://www.w3.org/2001/XMLSchema-instance"
xmlns:b="http://schemas.datacontract.org/2004/07/CPR.DMS.BusinessEntity">
<_isDirty
xmlns="http://schemas.datacontract.org/2004/07/CPR.DMS.Framework.Business">false</_isDirty>
<_systemID
xmlns="http://schemas.datacontract.org/2004/07/CPR.DMS.Framework.Business">fa61c113-181
8-4d6e-9bd5-e983bcd2895b</_systemID>
<_systemParentID i:nil="true"
xmlns="http://schemas.datacontract.org/2004/07/CPR.DMS.Framework.Business"></_systemParentID>
<b:Answer i:nil="true"></b:Answer>
<b:IsLoggedIn>true</b:IsLoggedIn>
<b:LastLogonDateTime>2008-03-26T13:30:29.573</b:LastLogonDateTime>
<b:LogonDateTime>2008-03-26T13:30:29.573</b:LogonDateTime>
<b:Pin>32622</b:Pin>
<b:Question i:nil="true"></b:Question>
<b:SystemRights>ReadOnly</b:SystemRights>
<b:UserID>10001</b:UserID>
<b:UserType>2</b:UserType>
<b:WebUserType>CounselingClient</b:WebUserType>
</ResponseObject>
</ResponseEntity>
</s:Body>
</s:Envelope>
</MessageLogTraceRecord>

I am not sure why this Message is not serialize correctly. I have set up all
the attributes Dtaacontracts, DataMembers, Etc.

and the web.config looks like:

<system.serviceModel>
   <diagnostics>
     <messageLogging logEntireMessage="true" logMalformedMessages="true"
       logMessagesAtTransportLevel="true" maxMessagesToLog="50000000"
       maxSizeOfMessageToLog="50000000" />
   </diagnostics>
   <bindings>
     <wsHttpBinding>
       <binding name="TransportSecurity">
         <security mode="TransportWithMessageCredential">
           <transport clientCredentialType="Windows"
proxyCredentialType="None"
                realm="" />
           <message clientCredentialType="Windows"
negotiateServiceCredential="true" algorithmSuite="Default"
establishSecurityContext="true" />
         </security>
       </binding>
     </wsHttpBinding>
   </bindings>
   <services>
     <service
behaviorConfiguration="CPR.DMS.Server.Service.UserServiceBehavior"
       name="CPR.DMS.Server.Service.UserService">
       <endpoint address="https://localhost/DMSRemoteAgency/UserService.svc"
         binding="wsHttpBinding" bindingConfiguration="TransportSecurity"
         contract="CPR.DMS.Server.Service.IUserService" />
       <endpoint address="mex" binding="mexHttpsBinding"
contract="IMetadataExchange" />
       <host>
         <timeouts closeTimeout="00:01:10" openTimeout="00:05:00" />
       </host>
     </service>      
   </services>
   <behaviors>
     <serviceBehaviors>
       <behavior name="CPR.DMS.Server.Service.UserServiceBehavior">
         <serviceMetadata httpsGetEnabled="true" />
         <serviceDebug includeExceptionDetailInFaults="true" />
       </behavior>
     </serviceBehaviors>
   </behaviors>
 </system.serviceModel>

I generate the Client proxy using Visual Studio 2008 and what I believe
should be causing problems is on the following lines:

[System.Diagnostics.DebuggerStepThroughAttribute()]
   
[System.CodeDom.Compiler.GeneratedCodeAttribute("System.Runtime.Serialization", "3.0.0.0")]
   
[System.Runtime.Serialization.CollectionDataContractAttribute(Name="EntityPropertyCollection",
Namespace="http://schemas.datacontract.org/2004/07/CPR.DMS.Framework.Business", ItemName="anyType")]
   [System.SerializableAttribute()]
   public class EntityPropertyCollection :
System.Collections.Generic.List<object> {
   }
   
   [System.CodeDom.Compiler.GeneratedCodeAttribute("System.ServiceModel",
"3.0.0.0")]
   
[System.ServiceModel.ServiceContractAttribute(Namespace="http://www.cprops.com/", ConfigurationName="UserService.IUserService")]
   public interface IUserService {
       
       // CODEGEN: Generating message contract since the wrapper name
(RequestEntity) of message RequestEntity does not match the default value
(LoginUser)
       
[System.ServiceModel.OperationContractAttribute(Action="http://www.cprops.com/IUserService/LoginUser",
ReplyAction="http://www.cprops.com/IUserService/LoginUserResponse")]
       [System.ServiceModel.ServiceKnownTypeAttribute(typeof(object[]))]
       
[System.ServiceModel.ServiceKnownTypeAttribute(typeof(CPR.DMS.Framework.Business.BusinessEntity))]
       
[System.ServiceModel.ServiceKnownTypeAttribute(typeof(CPR.DMS.ClientProxy.UserService.EntityPropertyCollection))]
       
[System.ServiceModel.ServiceKnownTypeAttribute(typeof(CPR.DMS.BusinessEntity.User))]
       
[System.ServiceModel.ServiceKnownTypeAttribute(typeof(CPR.DMS.BusinessEntity.SystemRights))]
       
[System.ServiceModel.ServiceKnownTypeAttribute(typeof(CPR.DMS.BusinessEntity.WebUserType))]
       CPR.DMS.ClientProxy.UserService.ResponseEntity
LoginUser(CPR.DMS.ClientProxy.UserService.RequestEntity request);
   }

The line: public class EntityPropertyCollection :
System.Collections.Generic.List<object> {
and the line
[System.ServiceModel.ServiceKnownTypeAttribute(typeof(object[]))] must be the
reason why I am getting the error:

{"Type 'System.Object[]' cannot be added to list of known types since
another type 'System.Collections.ArrayList' with the same data contract name
'http://schemas.microsoft.com/2003/10/Serialization/Arrays:ArrayOfanyType' is
already present."}

The user Object looks like:

[Serializable]
   [KnownType(typeof(WebUserType))]
   [DataContract]
   public partial class User : CPR.DMS.Framework.Business.BusinessEntity
   {

       #region "PRIVATE DECLARATIONS"

       internal protected EntityProperty<String> _userID =
(EntityProperty<String>)_propertyCollection.Add(new
EntityProperty<String>("UserID", EntityPropertyOptions.IsRequired, new
StringValidator(0, 50)));
       internal protected EntityProperty<Int32> _userType =
(EntityProperty<Int32>)_propertyCollection.Add(new
EntityProperty<Int32>("UserType"));
       internal protected EntityProperty<String> _pin =
(EntityProperty<String>)_propertyCollection.Add(new
EntityProperty<String>("Pin", new StringValidator(0, 50)));
       internal protected EntityProperty<String> _question =
(EntityProperty<String>)_propertyCollection.Add(new
EntityProperty<String>("Question", new StringValidator(0, 50)));
       internal protected EntityProperty<String> _answer =
(EntityProperty<String>)_propertyCollection.Add(new
EntityProperty<String>("Answer", new StringValidator(0, 50)));
       internal protected EntityProperty<DateTime?> _lastLogonDateTime =
(EntityProperty<DateTime?>)_propertyCollection.Add(new
EntityProperty<DateTime?>("LogonDateTime"));
       internal protected EntityProperty<WebUserType> _webUserType =
(EntityProperty<WebUserType>)_propertyCollection.Add(new
EntityProperty<WebUserType>("WebUserType"));
       
       #endregion

       #region "PROPERTY DECLARATIONS"
       [DataMember]
       public String UserID
       {
           get { return _userID.Value; }
           set { _userID.Value = value;  }
       }
       [DataMember]
       public Int32 UserType
       {
           get { return _userType.Value; }
           set { _userType.Value = value; }
       }
       [DataMember]
       public String Pin
       {
           get { return _pin.Value; }
           set { _pin.Value = value;}
       }
       [DataMember]
       public String Question
       {
           get { return _question.Value; }
           set { _question.Value = value;}
       }
       [DataMember]
       public String Answer
       {
           get { return _answer.Value; }
           set {_answer.Value = value; }
       }
       [DataMember]
       public DateTime? LastLogonDateTime
       {
           get { return _lastLogonDateTime.Value; }
           set { _lastLogonDateTime.Value = value; }
       }
       [DataMember]
       public WebUserType WebUserType
       {
           get { return _webUserType.Value; }
           set { _webUserType.Value = value; }
       }

       #endregion

       [OnDeserializingAttribute()]
       public void Init(StreamingContext context)
       {
           _userID = (EntityProperty<String>)_propertyCollection.Add(new
EntityProperty<String>("UserID", EntityPropertyOptions.IsRequired, new
StringValidator(0, 50)));
           _userType = (EntityProperty<Int32>)_propertyCollection.Add(new
EntityProperty<Int32>("UserType"));
           _pin = (EntityProperty<String>)_propertyCollection.Add(new
EntityProperty<String>("Pin", new StringValidator(0, 50)));
           _question = (EntityProperty<String>)_propertyCollection.Add(new
EntityProperty<String>("Question", new StringValidator(0, 50)));
           _answer = (EntityProperty<String>)_propertyCollection.Add(new
EntityProperty<String>("Answer", new StringValidator(0, 50)));
           _lastLogonDateTime =
(EntityProperty<DateTime?>)_propertyCollection.Add(new
EntityProperty<DateTime?>("LogonDateTime"));
           _webUserType =
(EntityProperty<WebUserType>)_propertyCollection.Add(new
EntityProperty<WebUserType>("WebUserType"));

       }

   }

Any Ideas why I might be getting this error?

Thanks