Fault Contract in WCF

What is fault Contract?

A Fault Contract is a way to handle an error/exception in WCF. In C# we can handle the error using try and catch blocks at the client side. The purpose of a Fault Contract is to handle an error by the service class and display in the client side. Whenever the client makes a call to a service class and an unexpected exception comes such as, SQL Server is not responding, or Divide by zero; in this case the service class throws an exception to the client using the Fault Contract. 

By default when we throw an exception from a service, it will not reach the client. WCF provides the option to handle and convey the error message to the client from a service using a SOAP Fault Contract.

To support SOAP Faults, WCF provides the FaultException class. This class has two forms:

1. FaultException: to send an untyped fault back to the caller
2. FaultException<T>: to send a typed fault data to the client. It is basically a Generic Type.

Syntax 

[OperationContract]

[FaultContract(typeof(MyException))]

string getDetails(int value);

The Fault Contract sample demonstrates how to communicate error information from a service to a client. The sample is based on the, with some additional code added to the servie to convert an internal exception to a fault.

Now we are going to implement the Fault Contract .

Create a new Project . add  WCF Application Project. the Code are :

using System.Runtime.Serialization;

using System.ServiceModel;

using System.ServiceModel.Web;

using System.Text;

namespace FaultContractApp

{

    [ServiceContract]

    public interface IService1

    {

        [OperationContract]

        [FaultContract (typeof(CustomException))]

        int add(int num1, int num2);

    }

    [DataContract()]

    public class CustomException

    {

        [DataMember()]

        public string Title;

        [DataMember()]

        public string ExceptionMessage;

        [DataMember()]

        public string InnerException;

        [DataMember()]

        public string StackTrace;

    }

using System.Runtime.Serialization;

using System.ServiceModel;

using System.ServiceModel.Web;

using System.Text;

namespace FaultContractApp

{

    public class Service1 : IService1

    {

        public int add(int num1, int num2)

        {

            CustomException _fault = new CustomException();

            _fault.ExceptionMessage = "Exception occured in the service!";

            _fault.InnerException = "Inner EXception";

            _fault.Title = "Exception Title";

            _fault.StackTrace = "Stack Trace message from service.";

            throw new FaultException<CustomException>(_fault,"Reason: Testing the Fault contract");

        }

    }

}

now add a new Console Project in your Solution. add the ServiceReference in your Console Project .

now write the Code to use Service . the Code are :

using System.ServiceModel;

using myConsole.ServiceReference1;

namespace myConsole

{

    class Program

    {

        static void Main(string[] args)

        {

            Service1Client _service = new Service1Client();

            try

            {

                int result = _service.add(11, 55);

                Console.WriteLine(result);

                Console.ReadLine();

            }

            catch (FaultException<CustomException> ex)

            {

                Console.WriteLine(string.Format("Title ->  {0} ", ex.Detail.Title));

                Console.WriteLine(string.Format("ExceptionMessage ->  {0} ", ex.Detail.ExceptionMessage));

                Console.WriteLine(string.Format("Inner Exception ->  {0} ", ex.Detail.InnerException));

                Console.WriteLine(string.Format("StackTrace ->  {0} ", ex.Detail.StackTrace));

                Console.ReadLine();

            }

        }

    }

}

Now debug the Console Application. you will get the Fault Exception generated by Service end.

the Complete Demo Project is attached: Click me!