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WCF: Data Contract Names: Don't Use Names with the "Response" Suffix

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After creating simple WCF service I've got strange errors (see below).

 

The issue was in the names of the response messages.

I used the simple custom rule to name request and response messages (.NET DataContract classes). I used Request and Response as suffixes:

<OperationName>Request and <OperationName>Response

For instance I created GetTokenResponse class for the response message of the GetToken operation.

 

And this is the wrong rule!

Why? Because the WCF creates the same names from the WSDL metadata files:

 

For instance I've got:

...

<wsdl:message name="ITokenStore_GetToken_OutputMessage">

** ** <wsdl:part name="parameters" element="tns:GetTokenResponse" /> ...

 

....<wsdl:operation name="GetToken">

** ** <wsdl:input wsaw:Action=http://mycompany.services/TokenStore/2008-05-29/ITokenStore/GetToken message="tns:ITokenStore_GetToken_InputMessage" />

** ** <wsdl:output wsaw:Action=http://MyServices/TokenStore/2008-05-29/ITokenStore/GetTokenResponse message="tns:ITokenStore_GetToken_OutputMessage" />

 

 

When I changed the name to the GetToken_Response the errors disappeared.

It is not an error in the WCF it is just undocumented feature.

The problem is the error text gives us unhelpful and ambiguous information.

 

See the article in MSDN. Not a clue about these rules.

 

Conclusion:

  • Don't use the messages names with suffixes Response, Solicit, Request.

  • Don't use the name convention for the request and response messages (.NET classes) like <OperationName>Request and <OperationName>Response !

 

This behavior is because of the WSDL standard.

See  http://www.w3.org/TR/wsdl#_names

"

2.4.5 Names of Elements within an Operation

The name attribute of the input and output elements provides a unique name among all input and output elements within the enclosing port type.

In order to avoid having to name each input and output element within an operation, WSDL provides some default values based on the operation name. If the name attribute is not specified on a one-way or notification message, it defaults to the name of the operation. If the name attribute is not specified on the input or output messages of a request-response or solicit-response operation, the name defaults to the name of the operation with "Request"/"Solicit" or "Response" appended, respectively.

"

Error in SoapUI

, when we've tried to get the metadata:

... ERROR:javax.wsdl.WSDLException: WSDLException (at /HTML): faultCode=INVALID_WSDL: Expected element '{http://schemas.xmlsoap.org/wsdl/%7Ddefinitions'.

 

Error in IE: by address the <ServiceAddressURL>

The service encountered an error.

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: http://MyServices/TokenStore/2008-05-29:ITokenStore ----> System.Xml.Schema.XmlSchemaException: The global element 'http://MyServices/TokenStore/2008-05-29:GetTokenResponse' has already been declared.
   at System.Xml.Schema.XmlSchemaSet.InternalValidationCallback(Object sender, ValidationEventArgs e)
   at System.Xml.Schema.BaseProcessor.AddToTable(XmlSchemaObjectTable table, XmlQualifiedName qname, XmlSchemaObject item)
   at System.Xml.Schema.Preprocessor.Preprocess(XmlSchema schema, String targetNamespace, ArrayList imports)
   at System.Xml.Schema.Preprocessor.Execute(XmlSchema schema, String targetNamespace, Boolean loadExternals)
   at System.Xml.Schema.XmlSchemaSet.PreprocessSchema(XmlSchema& schema, String targetNamespace)
   at System.Xml.Schema.XmlSchemaSet.Reprocess(XmlSchema schema)
   at System.ServiceModel.Description.MessageContractExporter.Compile()
   at System.ServiceModel.Description.DataContractSerializerMessageContractExporter.Compile()
   at System.ServiceModel.Description.MessageContractExporter.ExportMessage(Int32 messageIndex, Object state)
   at System.ServiceModel.Description.MessageContractExporter.ExportMessageContract()
   at System.ServiceModel.Description.WsdlExporter.CallExtension(WsdlContractConversionContext contractContext, IWsdlExportExtension extension)
   --- End of inner ExceptionDetail stack trace ---
   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 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.MessageRpc.Process(Boolean isOperationContextSet)

Error in IE: by address the <ServiceAddressURL>?wsdl

The service encountered an error.

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: http://MyServices/TokenStore/2008-05-29:ITokenStore ----> System.Xml.Schema.XmlSchemaException: The global element 'http://MyServices/TokenStore/2008-05-29:GetTokenResponse' has already been declared.
   at System.Xml.Schema.XmlSchemaSet.InternalValidationCallback(Object sender, ValidationEventArgs e)
   at System.Xml.Schema.BaseProcessor.AddToTable(XmlSchemaObjectTable table, XmlQualifiedName qname, XmlSchemaObject item)
   at System.Xml.Schema.Preprocessor.Preprocess(XmlSchema schema, String targetNamespace, ArrayList imports)
   at System.Xml.Schema.Preprocessor.Execute(XmlSchema schema, String targetNamespace, Boolean loadExternals)
   at System.Xml.Schema.XmlSchemaSet.PreprocessSchema(XmlSchema& schema, String targetNamespace)
   at System.Xml.Schema.XmlSchemaSet.Reprocess(XmlSchema schema)
   at System.ServiceModel.Description.MessageContractExporter.Compile()
   at System.ServiceModel.Description.DataContractSerializerMessageContractExporter.Compile()
   at System.ServiceModel.Description.MessageContractExporter.ExportMessage(Int32 messageIndex, Object state)
   at System.ServiceModel.Description.MessageContractExporter.ExportMessageContract()
   at System.ServiceModel.Description.WsdlExporter.CallExtension(WsdlContractConversionContext contractContext, IWsdlExportExtension extension)
   --- End of inner ExceptionDetail stack trace ---
   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.TryHandleMetadataRequest(Message httpGetRequest, String[] queries, Message& replyMessage)
   at System.ServiceModel.Description.ServiceMetadataExtension.HttpGetImpl.ProcessHttpRequest(Message httpGetRequest)
   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.MessageRpc.Process(Boolean isOperationContextSet)