WCF service in WPF self host application crash when I throw a fault exception (async methods)

Question

I have a service hosted in a WPF application with an async method with the Begin/end methods, and when I catch an exception in the service, I want to throw a faultException to warn to the client.

However, when I try to throw the faultException, the host application crash, shutdown suddenly.

In my repository, I catch the UpdateException, then, I create a custom exception, UniqueKeyException, that is throw to the caller. The caller is an auxiliar method that is called in the Begin method.

This auxiliar method, catch the UniqyeKeyException and only do a "throw", that is capture in the try/catch block of my end method. Here there is something that I don't understand, why in the end mehod this exception is catched in the block of AgregateException instead of the UniqueKeyException.

Well, anyway, in the catch block of the end method, in the AgregateException block, I check if the innerException is UniqueKeyException, if it is true, I create an object UniqueKeyArgs (a custom class with the information to send to the client), create a FaultException and finally do the throw FaultException. It is in this step, the throw, where the host application crash.

I think that I have all configure correctly, because my custom class UniqueKeyArgs is decorate as Datacontract and its properties as DataMember, in the app.config of my host application I configure the behavior to include exception details and in the contract I decorate it with faultContract.

Why the application crash?

My code is the following:

REPOSITORY

public List<Usuers> updateUsers(List<Users> paramUsers)
{
....

catch(UpdateException ex)
{
SqlException innerEx = (SqlException)ex.InnerException;

                //Code 2627 is Unique Key exception from SQL Server.
                if (innerEx != null && innerEx.Number == 2627)
                {
                    //I create the conditions of searching
                    ConditionsUsers conditions = new conditions();

                    conditions.UserName = (Users)ex.StateEntries[0].Entity).userName;

                    //Search for the existing user
                    Users myUser = getUser(conditions);
                    string message = "the user " + conditions.userName + " exists.";
                    throw new UniqueKeyException(message, myUser);
                }
                throw;
}

SERVICE IMPLEMENTATION

//This is my auxiliar method, called in the Begin method.
private submitUpdates()
{
     ....

     catch(UniqueKeyException ex)
     {
          //The code enter here
          throw;
     }
}



public IAsyncResult BeginUpdateUsers(List<users> paramUsers, AsyncCallback callback, object state)
{
     Task<List<Users>> myTask= Task<List<Users>>.Factory.StartNew(p => sumbmitUpdates(paramUsers), state);
     return myTask.ContinueWith(res => callback(myTask));
}


public List<Users> EndUpdateusers(IAsyncResult result)
     {
          try
          {
               return ((Task<List<Users>>)result).Result;
          }
          //Why agregateException and not is catched in  the UniqueKeyException ???
          catch(AgregateException ex)
          {
               if (innerExceptions[0] is UsuariosValorUnicoException)
                    {
                        //I assign manually the data to debug, to discard other problems.
                        Users myUser = new Users();
                        myUser.UserName = "Jhon";
                        myUser.Password = "pass123";
                        UniqueKeyArgs myArgs = new UniqueUserArgs("unique key error", myUser);
                        FaultException<UniqueKeyArgs> myException = new FaultException<UniqueKeyArgs>(myArgs);

                        //Crash here, in the throw myException
                        throw myException;                        
                    }
                }
                throw;
          }

MY CONTRACT

[FaultContract(typeof(UniqueKeyArgs))]
IAsyncResult BeginUpdateUsers(List<Users> paramUser, AsyncCallback callback, object state);
List<Users> EndUpdateUsers(IAsyncResult result);

Crash when I throw myException in the End method.

I see in this post that the solution is catch the exception in the host application too, not only in the service object. However, this solution uses Application.ThreadException, that belong to System.Windows.Forms namespace, and I am using a WPF application.

How could I send the exception to the client from a service hosted in a WPF application?

Thanks.

EDIT1: well, I am use a try/catch block in the line where I throw the exception and I see that the error is that I have not indicated a reason, so when I create my FaultException I do:

FaultException<UniqueKeyArgs> myException = new FaultException<UniqueKeyArgs>(myArgs, new FaultReason("DummyReason");

In this case, the exception message is "DummyReason", the message that I set in the FaultReason, so it says me nothing. The FaultException is not throw, and throw the generic exception to the client.

In this case the host application does not shutdown, but close the connection with the client and I have to reconnect.

It seems that the problem is the creaton of the FaultException, but I don't see the problem.

@Roeal suggests that perhaps is only possible to use faultException with synch methods, but in this link I can see an example in which is used with async methods. I have seen others examples, is not the unique.

Thanks.

EDIT2: I solve my problem. My problem is that in the FaultException, T is an object that have a property that was a self tracking entity, and this is a problem, if I am not wrong, I only can use basic types as properties of the exception.

Then, in the exception, I have implmemented ISerialize. It's needed to be able to send the information to the client, without this, the client receives an exception.Detail with null properties.

Answer 1

I solve my problem. My problem is that in the FaultException, T is an object that have a property that was a self tracking entity, and this is a problem, if I am not wrong, I only can use basic types as properties of the exception.

Then, in the exception, I have implmemented ISerialize. It's needed to be able to send the information to the client, without this, the client receives an exception.Detail with null properties.

Answer 2

Did you also declare the synchronous operation in your service contract? In that case, maybe this helps:

If fault contracts are defined on the service operation contract, the FaultContract attribute should be applied only on the synchronous operations.
-- Juval Lowy, "Programming WCF Services 3rd Edition" (p456)