How to Implement 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 service to convert an internal exception to a fault.

 

What is the use of FaultContract?

 

In ASP.Net, C#, and VB.Net it's very simple to handle an exception just by adding the simple Try & Catch blocks. But when you talk about the WCF Service if an unexpected error occurs (like Server not responding properly and divide by zero) in a WCF Service then the exception details can be passed to the client using a Fault Contract.

 

FaultContract inherits from the FaultContractAttribute Class.

 

 

 

Now we are going to implement the Fault Contract with database connectivity

 

Step 1: Database Setup

 

Create a table named EMPLOYEE with column names EMP_ID and EMP_NAME. We will create a service to input the user id and get the name of the employee. 

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO

CREATE TABLE [DBO].[EMPLOYEE](

          [EMP_ID] [INT] NULL,

          [EMP_NAME] [VARCHAR](50) NULL

) ON [PRIMARY]

GO
SET ANSI_PADDING OFF
GO

INSERT INTO EMPLOYEE(EMP_ID,EMP_NAME) VALUES(1,'AMIT')
INSERT INTO EMPLOYEE(EMP_ID,EMP_NAME) VALUES(2,'KIRTI')

Step 2: Open Visual Studio then select "File" -> "New" -> "Project..." -> "WCF" -> "WCF Service Application".

 

1. Create IService.cs and Service.cs.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Web;
using System.Text;
[ServiceContract]
public interface IService
{
    [OperationContract]
    [FaultContract(typeof(MyException))]
    string getDetails(int value);
}
[DataContract]
public class MyException
{
    private string strReason;
    public string Reason
    {
        get { return strReason; }
        set { Reason = value; }
    }
}

Service.cs

public class Service: IService
{
 public string GetData(int value)
 {
  return string.Format("You entered: {0}", value);
 }
 string r = null;
 public string getDetails(int id)
 {
  try
  {
   SqlConnection con = new SqlConnection(@ "Data Source=AMIT-PC\MIND;Initial Catalog=wcf;Integrated Security=False;uid=sa;pwd=Mind1234");
   con.Open();
   SqlCommand cmd = new SqlCommand("SELECT EMP_NAME FROM EMPLOYEE WHERE EMP_ID= " + id + "", con);
   SqlDataReader rd = cmd.ExecuteReader();
   while (rd.Read())
   {
    if (rd == null)
    {
    } else
    {
     r = rd["EMP_NAME"].ToString();
    }
   }
   return r;
  } catch (Exception e)
  {
   MyException m = new MyException();
   m.Reason = "Some Problem";
   throw new FaultException < MyException > (m);
  }
 }
}