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
  1. [OperationContract]
  2. [FaultContract(typeof(MyException))]
  3. 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.
WCF.jpg
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.
  1. SET ANSI_NULLS ON
  2. GO
  3. SET QUOTED_IDENTIFIER ON
  4. GO
  5. SET ANSI_PADDING ON
  6. GO
  8. CREATE TABLE [DBO].[EMPLOYEE](
  10. [EMP_ID] [INT] NULL,
  12. [EMP_NAME] [VARCHAR](50) NULL
  14. ) ON [PRIMARY]
  16. GO
  17. SET ANSI_PADDING OFF
  18. GO
  20. INSERT INTO EMPLOYEE(EMP_ID,EMP_NAME) VALUES(1,'AMIT')
  21. 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.
  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4. using System.Runtime.Serialization;
  5. using System.ServiceModel;
  6. using System.ServiceModel.Web;
  7. using System.Text;
  8. [ServiceContract]
  9. public interface IService
  10. {
  11. [OperationContract]
  12. [FaultContract(typeof(MyException))]
  13. string getDetails(int value);
  14. }
  15. [DataContract]
  16. public class MyException
  17. {
  18. private string strReason;
  19. public string Reason
  20. {
  21. get { return strReason; }
  22. set { Reason = value; }
  23. }
  24. }
Service.cs
  1. public class Service: IService
  2. {
  3. public string GetData(int value)
  4. {
  5. return string.Format("You entered: {0}", value);
  6. }
  7. string r = null;
  8. public string getDetails(int id)
  9. {
  10. try
  11. {
  12. SqlConnection con = new SqlConnection(@ "Data Source=AMIT-PC\MIND;Initial Catalog=wcf;Integrated Security=False;uid=sa;pwd=Mind1234");
  13. con.Open();
  14. SqlCommand cmd = new SqlCommand("SELECT EMP_NAME FROM EMPLOYEE WHERE EMP_ID= " + id + "", con);
  15. SqlDataReader rd = cmd.ExecuteReader();
  16. while (rd.Read())
  17. {
  18. if (rd == null)
  19. {
  20. } else
  21. {
  22. r = rd["EMP_NAME"].ToString();
  23. }
  24. }
  25. return r;
  26. } catch (Exception e)
  27. {
  28. MyException m = new MyException();
  29. m.Reason = "Some Problem";
  30. throw new FaultException < MyException > (m);
  31. }
  32. }
  33. }