Exception Handling in WCF using Fault Contract

Introduction

In all managed applications, processing errors are represented by Exception objects. In WCF applications, service methods communicate processing error information using SOAP fault messages. SOAP faults are message types that are included in the metadata for a service operation and, therefore, create a fault contract that clients can use to make their operation more interactive. In addition, because SOAP faults are expressed to clients in XML form,theyare highly interoperable.

To be more concrete,let us start with anexample:

Create an empty solution in VS2005 called "IndigoException". Add one project called "IndigoService". Nexta dd a reference to System.ServiceModel and then a dd an interface.

using System;

using System.Collections.Generic;

using System.Text;

using System.ServiceModel;

using System.Runtime.Serialization;

namespace Indigo

{

[ServiceContract()]

public interface IService

{

[OperationContract]

[FaultContract(typeof (MyFaultException))]

string GetMessage();

}
}

Add one more class as follows:

using System;

using System.Text;

using System.Runtime.Serialization;

namespace Indigo

{

[DataContract]

public class MyFaultException

{

private string _reason;

[DataMember]

public string Reason

{

get { return _reason; }

set { _reason = value ; }

}

}

}

Add one class "Service" and a reference to System.ServiceModel

using System;

using System.Collections.Generic;

using System.Text;

using System.ServiceModel;

namespace Indigo

{

public class Service : IService

{

#region IService Members

public string GetMessage()

{

try

{

int i, j, k;

j = 1;

k = 0;

i = j / k;

}

catch (Exception exp)

{

MyFaultException theFault = new MyFaultException();

theFault.Reason = "Some Error " + exp.Message.ToString();

throw new FaultException<MyFaultException>(theFault);

}

return "No Error" ;

}

#endregion

}

}

Build the project.

Now add another project "Host" and add reference to "IndigoService" project and to System.ServiceModel

using System;

using System.Collections.Generic;

using System.Text;

using System.ServiceModel;

namespace Indigo

{

class IndigoHost

{

internal static ServiceHost myServiceHost = null ;

static void Main(string [] args)

{

StartService();

Console .WriteLine("Service at your service" );

Console .ReadKey();

StopService();

}

internal static void StartService()

{

myServiceHost = new ServiceHost(typeof (Indigo.Service));

myServiceHost.Open();

}

internal static void StopService()

{

//Call StopService from your shutdown logic (i.e. dispose method)

if (myServiceHost.State != CommunicationState.Closed)

myServiceHost.Close();

}

}

}

Add app.config with the following XML:

<? xml version = "1.0 " encoding = "utf-8 " ?>

< configuration >

< system.serviceModel >

< services >

< service behaviorConfiguration = "MyServiceTypeBehaviors " name = "Indigo.Service ">

< endpoint address = "Service " binding = "wsHttpBinding " contract = "Indigo.IService " />

< host >

< baseAddresses >

< add baseAddress = "http://localhost:1111/Indigo " />

</ baseAddresses >

</ host >

</ service >

</ services >

< behaviors >

< serviceBehaviors >

< behavior name = "MyServiceTypeBehaviors ">

< serviceMetadata httpGetEnabled = "true " />

< serviceDebug includeExceptionDetailInFaults = "true " />

</ behavior >

</ serviceBehaviors >

</ behaviors >

</ system.serviceModel >
</ configuration >

Build the project. Run Host.exe from VS2005 command prompt. You should get the messageat thecommand prompt as follows:



Add another project "IndigoClient" and add System.ServiceModel

Now add service refrence to the service URL (i.e. http://localhost:1111/Indigo )

It will create localhost.cs in service reference.

Add a class Program.cs as follows:

using System;

using System.Collections.Generic;

using System.Text;

using System.ServiceModel;

namespace Indigo

{

class Program

{

static void Main(string [] args)

{

string result = "" ;

try

{

IndigoClient.localhost.IService ww = new IndigoClient.localhost.ServiceClient
();

result = ww.GetMessage();

}

catch (FaultException<IndigoClient.localhost.MyFaultException> ee)

{

result = "Exception: " + ee.Detail.Reason;

}

Console .WriteLine(result);

Console .ReadLine();

}

}

}

Add app.config with following XML

<? xml version = "1.0 " encoding = "utf-8 " ?>

< configuration >

< system.serviceModel >

< bindings >

< wsHttpBinding >

< binding