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POWCF DataContractSerializer
 

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  1. POWCF DataContractSerializer
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    <p>I am getting the following error when trying to return a Questionnaire object to the client. I added the KnowType[typeof(...)] in the Data Contract as suggested, but it still doesn't work. Not knowing which type is unknown to the Serializer, I just threw in all classes that are in the EF model. Can someone help? Thanks.</p> <p>Here is the Service Contract</p> <pre><code>using System; using System.Collections.Generic; using System.Linq; using System.Runtime.Serialization; using System.ServiceModel; using System.ServiceModel.Web; using System.Text; using QuestionnaireWcfServiceApp.Models; namespace QuestionnaireWcfService { [ServiceContract] public interface IQuestionnaireService { [OperationContract] QuestionnaireContract GetQuestionnaire(string questionnaireName); [OperationContract] QuestionChain LoadQuestion(int questionnaireID, int? questionID, int? userResponse); } [DataContract] [KnownType(typeof(Questionnaire))] [KnownType(typeof(Question))] [KnownType(typeof(Choice))] [KnownType(typeof(Decision))] [KnownType(typeof(QuestionFlow))] public class QuestionChain { [DataMember] public Question Question { get; set; } [DataMember] public int? Decision {get;set;} } [DataContract] [KnownType(typeof(Questionnaire))] [KnownType(typeof(Question))] [KnownType(typeof(Choice))] [KnownType(typeof(Decision))] [KnownType(typeof(QuestionFlow))] public class QuestionnaireContract { [DataMember] public Questionnaire Questionnaire { get; set; } } } </code></pre> <p>Here is the Service.</p> <pre><code>using System; using System.Collections.Generic; using System.Linq; using System.Runtime.Serialization; using System.ServiceModel; using System.ServiceModel.Web; using System.Text; using QuestionnaireWcfServiceApp.Models; namespace QuestionnaireWcfService { public class QuestionnaireService : IQuestionnaireService { QuestionnaireWcfServiceApp.Models.QuestionnaireEntities db = new QuestionnaireEntities(); public QuestionnaireContract GetQuestionnaire(string questionnaireName) { QuestionnaireContract questionnaireContract = new QuestionnaireContract(); if (!string.IsNullOrEmpty(questionnaireName)) { Questionnaire thisQuestionnaire = (from q in db.Questionnaires where q.Name.Equals(questionnaireName) select q).FirstOrDefault(); if (thisQuestionnaire == null) throw new ArgumentNullException("Questionnaire ID is not found."); else { questionnaireContract.Questionnaire = thisQuestionnaire; return questionnaireContract; } } else throw new ArgumentException("Questionnaire name is not specified."); } public QuestionChain LoadQuestion(int questionnaireID, int? currentQuestionID, int? userResponse) { QuestionChain qc = new QuestionChain(); QuestionFlow thisFlow = null; Question nextQuestion = null; Questionnaire thisQuestionnaire = (from q in db.Questionnaires where q.QuestionnaireId == questionnaireID select q).FirstOrDefault(); if (thisQuestionnaire == null) throw new ArgumentNullException("Questionnaire ID is not found"); //InvalidOperationException; if (currentQuestionID.HasValue) { //QuestionID should never be changed after setup. Change the QuestionText around the QuestionID Question thisQuestion = thisQuestionnaire.Questions.Where(q =&gt; q.PKey.Equals(currentQuestionID)).FirstOrDefault(); if (thisQuestion == null) throw new ArgumentNullException("Question ID is not found"); else { if (userResponse.HasValue) { thisFlow = thisQuestion.QuestionFlows.First(f =&gt; f.QuestionId.Equals(currentQuestionID) &amp;&amp; f.ChoiceId.Equals(userResponse)); if (thisFlow.Question1 != null) { nextQuestion = thisFlow.Question1; qc.Question = nextQuestion; } else { qc.Question = null; qc.Decision = thisFlow.Decision.Value; } } else { //can't happen. when reaches here, a userResponse must not be null } } } else { //default to question 1 nextQuestion = thisQuestionnaire.Questions.First(q =&gt; q.QuestionId.Equals(1)); if (nextQuestion == null) throw new ArgumentNullException("Question ID"); else qc.Question = nextQuestion; } return qc; } } } </code></pre> <p>This is the exception in the Windows Application Log.</p> <pre><code>Exception: System.ServiceModel.CommunicationException: There was an error while trying to serialize parameter http://tempuri.org/:GetQuestionnaireResult. The InnerException message was 'Type System.Data.Entity.DynamicProxies.Questionnaire_EF00247BEFB9F733C947A4C3E57FD12709E91510AC0DA534D137ED75FCCAC342' with data contract name 'Questionnaire_EF00247BEFB9F733C947A4C3E57FD12709E91510AC0DA534D137ED75FCCAC342: http://schemas.datacontract.org/2004/07/System.Data.Entity.DynamicProxies' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.'. Please see InnerException for more details. ---&gt; System.Runtime.Serialization.SerializationException: Type 'System.Data.Entity.DynamicProxies.Questionnaire_EF00247BEFB9F733C947A4C3E57FD12709E91510AC0DA534D137ED75FCCAC342' with data contract name 'Questionnaire_EF00247BEFB9F733C947A4C3E57FD12709E91510AC0DA534D137ED75FCCAC342:http://schemas.datacontract.org/2004/07/System.Data.Entity.DynamicProxies' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer. at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeAndVerifyType(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, Boolean verifyKnownType, RuntimeTypeHandle declaredTypeHandle, Type declaredType) at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithXsiTypeAtTopLevel(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle originalDeclaredTypeHandle, Type graphType) at System.Runtime.Serialization.DataContractSerializer.InternalWriteObjectContent(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver) at System.Runtime.Serialization.DataContractSerializer.InternalWriteObject(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver) at System.Runtime.Serialization.XmlObjectSerializer.WriteObjectHandleExceptions(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver) at System.Runtime.Serialization.XmlObjectSerializer.WriteObject(XmlDictionaryWriter writer, Object graph) at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeParameterPart(XmlDictionaryWriter writer, PartInfo part, Object graph) --- End of inner exception stack trace --- at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeParameterPart(XmlDictionaryWriter writer, PartInfo part, Object graph) at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeParameter(XmlDictionaryWriter writer, PartInfo part, Object graph) at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeBody(XmlDictionaryWriter writer, MessageVersion version, String action, MessageDescription messageDescription, Object returnValue, Object[] parameters, Boolean isRequest) at System.ServiceModel.Dispatcher.OperationFormatter.SerializeBodyContents(XmlDictionaryWriter writer, MessageVersion version, Object[] parameters, Object returnValue, Boolean isRequest) at System.ServiceModel.Dispatcher.OperationFormatter.OperationFormatterMessage.OperationFormatterBodyWriter.OnWriteBodyContents(XmlDictionaryWriter writer) at System.ServiceModel.Channels.BodyWriterMessage.OnBodyToString(XmlDictionaryWriter writer) at System.ServiceModel.Channels.Message.ToString(XmlDictionaryWriter writer) at System.ServiceModel.Diagnostics.MessageLogTraceRecord.WriteTo(XmlWriter writer) at System.ServiceModel.Diagnostics.MessageLogger.LogInternal(MessageLogTraceRecord record) at System.ServiceModel.Diagnostics.MessageLogger.LogMessageImpl(Message&amp; message, XmlReader reader, MessageLoggingSource source) at System.ServiceModel.Diagnostics.MessageLogger.LogMessage(Message&amp; message, XmlReader reader, MessageLoggingSource source) Process Name: WebDev.WebServer40 Process ID: 11620 Event Xml: &lt;Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event"&gt; &lt;System&gt; &lt;Provider Name="System.ServiceModel 4.0.0.0" /&gt; &lt;EventID Qualifiers="49154"&gt;5&lt;/EventID&gt; &lt;Level&gt;2&lt;/Level&gt; &lt;Task&gt;7&lt;/Task&gt; &lt;Keywords&gt;0x80000000000000&lt;/Keywords&gt; &lt;TimeCreated SystemTime="2012-10-18T07:32:11.000000000Z" /&gt; &lt;EventRecordID&gt;36499&lt;/EventRecordID&gt; &lt;Channel&gt;Application&lt;/Channel&gt; &lt;Computer&gt;Jon-PC&lt;/Computer&gt; &lt;Security UserID="S-1-5-21-334737869-2079735299-2176000493-1000" /&gt; &lt;/System&gt; &lt;EventData&gt; &lt;Data&gt;System.ServiceModel.CommunicationException: There was an error while trying to serialize parameter http://tempuri.org/:GetQuestionnaireResult. The InnerException message was 'Type 'System.Data.Entity.DynamicProxies.Questionnaire_EF00247BEFB9F733C947A4C3E57FD12709E91510AC0DA534D137ED75FCCAC342' with data contract name 'Questionnaire_EF00247BEFB9F733C947A4C3E57FD12709E91510AC0DA534D137ED75FCCAC342:http://schemas.datacontract.org/2004/07/System.Data.Entity.DynamicProxies' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.'. Please see InnerException for more details. ---&amp;gt; System.Runtime.Serialization.SerializationException: Type 'System.Data.Entity.DynamicProxies.Questionnaire_EF00247BEFB9F733C947A4C3E57FD12709E91510AC0DA534D137ED75FCCAC342' with data contract name 'Questionnaire_EF00247BEFB9F733C947A4C3E57FD12709E91510AC0DA534D137ED75FCCAC342:http://schemas.datacontract.org/2004/07/System.Data.Entity.DynamicProxies' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer. at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeAndVerifyType(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, Boolean verifyKnownType, RuntimeTypeHandle declaredTypeHandle, Type declaredType) at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithXsiTypeAtTopLevel(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle originalDeclaredTypeHandle, Type graphType) at System.Runtime.Serialization.DataContractSerializer.InternalWriteObjectContent(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver) at System.Runtime.Serialization.DataContractSerializer.InternalWriteObject(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver) at System.Runtime.Serialization.XmlObjectSerializer.WriteObjectHandleExceptions(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver) at System.Runtime.Serialization.XmlObjectSerializer.WriteObject(XmlDictionaryWriter writer, Object graph) at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeParameterPart(XmlDictionaryWriter writer, PartInfo part, Object graph) --- End of inner exception stack trace --- at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeParameterPart(XmlDictionaryWriter writer, PartInfo part, Object graph) at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeParameter(XmlDictionaryWriter writer, PartInfo part, Object graph) at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeBody(XmlDictionaryWriter writer, MessageVersion version, String action, MessageDescription messageDescription, Object returnValue, Object[] parameters, Boolean isRequest) at System.ServiceModel.Dispatcher.OperationFormatter.SerializeBodyContents(XmlDictionaryWriter writer, MessageVersion version, Object[] parameters, Object returnValue, Boolean isRequest) at System.ServiceModel.Dispatcher.OperationFormatter.OperationFormatterMessage.OperationFormatterBodyWriter.OnWriteBodyContents(XmlDictionaryWriter writer) at System.ServiceModel.Channels.BodyWriterMessage.OnBodyToString(XmlDictionaryWriter writer) at System.ServiceModel.Channels.Message.ToString(XmlDictionaryWriter writer) at System.ServiceModel.Diagnostics.MessageLogTraceRecord.WriteTo(XmlWriter writer) at System.ServiceModel.Diagnostics.MessageLogger.LogInternal(MessageLogTraceRecord record) at System.ServiceModel.Diagnostics.MessageLogger.LogMessageImpl(Message&amp;amp; message, XmlReader reader, MessageLoggingSource source) at System.ServiceModel.Diagnostics.MessageLogger.LogMessage(Message&amp;amp; message, XmlReader reader, MessageLoggingSource source)&lt;/Data&gt; &lt;Data&gt;WebDev.WebServer40&lt;/Data&gt; &lt;Data&gt;11620&lt;/Data&gt; &lt;/EventData&gt; &lt;/Event&gt; </code></pre>
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    1. COMay be it is just my browser configuration (posted images seem to be filtered out), but I do not see any exception text. Could you please post the exception?
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    2. COI edited and reformatted the post. The exception is rather long. You need to use the vertical and horizontal scroll bars to view the full text. Thanks.
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    3. COIt looks like a lazily loaded object by EF which created a dynamic proxy at runtime which cannot be serialized. You should eagerly load all associations. And be careful because if you have circular dependencies in your object hierarchy it cannot be serialized either. The best way is to use data transfer objects and not expose your EF entities in the service contract.
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      1. USDarin Dimitrov
 

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