error in silverlight enabled webservice

hey guys, i made a silvelight enabled webservice in silverlight 2.0. i am trying to get data from database. but i m getting this error when i buid that service. does anyone know what is this problem. Models is my table name.

Thanks in advance.

An ExceptionDetail, likely created by IncludeExceptionDetailInFaults=true, whose value is:
System.InvalidOperationException: An exception was thrown in a call to a WSDL export extension: System.ServiceModel.Description.DataContractSerializerOperationBehavior
 contract: Service ----> System.Runtime.Serialization.InvalidDataContractException: Type 'Model' cannot be serialized. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want serialized with the DataMemberAttribute attribute.
   at System.Runtime.Serialization.DataContract.DataContractCriticalHelper.ThrowInvalidDataContractException(String message, Type type)
   at System.Runtime.Serialization.DataContract.DataContractCriticalHelper.CreateDataContract(Int32 id, RuntimeTypeHandle typeHandle, Type type)
   at System.Runtime.Serialization.DataContract.DataContractCriticalHelper.GetDataContractSkipValidation(Int32 id, RuntimeTypeHandle typeHandle, Type type)
   at System.Runtime.Serialization.DataContract.GetDataContractSkipValidation(Int32 id, RuntimeTypeHandle typeHandle, Type type)
   at System.Runtime.Serialization.DataContract.GetDataContract(RuntimeTypeHandle typeHandle, Type type, SerializationMode mode)
   at System.Runtime.Serialization.DataContract.GetDataContract(RuntimeTypeHandle typeHandle, Type type)
   at System.Runtime.Serialization.DataContract.GetDataContract(Type type)
   at System.Runtime.Serialization.DataContractSet.GetDataContract(Type clrType)
   at System.Runtime.Serialization.DataContractSet.AddCollectionDataContract(CollectionDataContract collectionDataContract)
   at System.Runtime.Serialization.DataContractSet.Add(XmlQualifiedName name, DataContract dataContract)
   at System.Runtime.Serialization.XsdDataContractExporter.Export(Type type)
   at System.ServiceModel.Description.MessageContractExporter.ExportType(Type type, String partName, String operationName, XmlSchemaType& xsdType)
   at System.ServiceModel.Description.DataContractSerializerMessageContractExporter.ExportBody(Int32 messageIndex, Object state)
   at System.ServiceModel.Description.MessageContractExporter.ExportMessage(Int32 messageIndex, Object state)
   at System.ServiceModel.Description.MessageContractExporter.ExportMessageContract()
   at System.ServiceModel.Description.DataContractSerializerOperationBehavior.System.ServiceModel.Description.IWsdlExportExtension.ExportContract(WsdlExporter exporter, WsdlContractConversionContext contractContext)
   at System.ServiceModel.Description.WsdlExporter.CallExtension(WsdlContractConversionContext contractContext, IWsdlExportExtension extension)
   --- End of inner ExceptionDetail stack trace ---
   at System.ServiceModel.Description.WsdlExporter.CallExtension(WsdlContractConversionContext contractContext, IWsdlExportExtension extension)
   at System.ServiceModel.Description.WsdlExporter.CallExportContract(WsdlContractConversionContext contractContext)
   at System.ServiceModel.Description.WsdlExporter.ExportContract(ContractDescription contract)
   at System.ServiceModel.Description.WsdlExporter.ExportEndpoint(ServiceEndpoint endpoint, XmlQualifiedName wsdlServiceQName)
   at System.ServiceModel.Description.WsdlExporter.ExportEndpoints(IEnumerable`1 endpoints, XmlQualifiedName wsdlServiceQName)
   at System.ServiceModel.Description.ServiceMetadataBehavior.MetadataExtensionInitializer.GenerateMetadata()
   at System.ServiceModel.Description.ServiceMetadataExtension.EnsureInitialized()
   at System.ServiceModel.Description.ServiceMetadataExtension.HttpGetImpl.InitializationData.InitializeFrom(ServiceMetadataExtension extension)
   at System.ServiceModel.Description.ServiceMetadataExtension.HttpGetImpl.GetInitData()
   at System.ServiceModel.Description.ServiceMetadataExtension.HttpGetImpl.TryHandleDocumentationRequest(Message httpGetRequest, String[] queries, Message& replyMessage)
   at System.ServiceModel.Description.ServiceMetadataExtension.HttpGetImpl.ProcessHttpRequest(Message httpGetRequest)
   at System.ServiceModel.Description.ServiceMetadataExtension.HttpGetImpl.Get(Message message)
   at SyncInvokeGet(Object , Object[] , Object[] )
   at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]& outputs)
   at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage4(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage3(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage2(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage1(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)