<ServiceContract()> _
Public Interface IService
<OperationContract()> _
<FaultContract(GetType(MyExceptionContainer))> _
Function div(ByVal num1 As Integer, ByVal num2 As Integer) As Integer
End Interface
<DataContract()> _
Public Class MyExceptionContainer
Dim msg, dsc As String
<DataMember()> _
Public Property message() As String
Get
Return msg
End Get
Set(ByVal value As String)
Msg = value
End Set
End Property
End Class
...............cs...........................
Public Class Service
Implements IService
Public Function div(ByVal num1 As Integer, ByVal num2 As Integer) As Integer Implements IService.div
Try
Return (num1 \ num2)
Catch ex As DivideByZeroException
Dim ec As New MyExceptionContainer
ec.message = "Error msg"
Throw New FaultException(Of MyExceptionContainer)(ec, New FaultReason(ec.message))
End Try
End Function
End Class
------------------.client Side ---------------------
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Try
Dim sr As New ServiceReference1.ServiceClient
Dim div As Integer = sr.div(10, 0)
Catch ex As FaultException(Of ServiceReference1.MyExceptionContainer)
Response.Write(ex.Detail.message)
End Try
End Sub
----------------------
Managing a correct error handling process in an application is a nightmare if you want to do it properly and I would say that it is not always the best exciting part, but it is absolutly needed to prevent as much as possible unhandle situation. In a normal application you simply place the code inside try-catch block with the exception type, and there are handle as normal .net exception object that you can bubble up.
With WCF service I have discover around different reading that it is a bit different, simply because WCF need to guaranty interoperability with any client application in order that they are able to catch error returned.
For that WCF need to convert the “normal .NEt exception” into a SOAP messageexception that will be understandable from client application.
To achive this you need to specify a FaultContract attrribute in your service either declaratively or imperatively way. For my case I have done it with declarative.
You specify the declarative FaultContrat as follow for your service method:
[OperationContract]
[FaultContract (typeof(MyError))]Boolean myMethod();
MyError is here a custom type which define an error message
After having configured the service FaultContractAttribute, next you need to raise the exception from your server side service method code as follow :
Server side
catch (Exception exc){
MyError ErrLog = new Maillefer.Nomos.Types.Common.MyError (“This is an error”,”Critical”); FaultException<MyError> fe = new FaultException<MyError >(ErrLog, new FaultReason(ErrLog.Message)); throw fe;}
So far so good. Then from the client application side you simply need to catch the FaultException error type as you normally do and retrive the message return by the Servcie SOAP message as follow:
Client side
catch (FaultException <MyError> MyError){ string msg = Error.Detail.Message; MessageBox.Show (msg);
wcfclient.Close();
}
And that’s it. You then receive the error message send from your server, inside your client application.. Hmmm this is what I was expecting but it was not behaving as expected. I spend days to cross check my code and verify impementation to get the exception correctly thrown but when runnig my application my service was stoping at the time it was throwing the exception (throw fe). The error return from that execution was something strange like :
“System.ServiceModel.FaultException`1 was unhandled by user code“
After a lot of research I find out the solution on a post mentionning that it was due to some setting ofdebugging scenario of my VS environement, which make my code execution stop at each exception with not really logic message wich was giving a lot of confusion.
To remove this behaviour it was advise to uncheck the 2 following options from the Tools->Option menu of IDE:
Please give the comment if the above solution save your time.
