Q8M1 – SC Dudy Fathan Ali S.Kom Distributed Application Development Exception Handling in WCF Services Dudy Fathan Ali, S.Kom (DFA) 2017 CEP - CCIT Fakultas Teknik Universitas Indonesia
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Q8M1 – SC Dudy Fathan Ali S.Kom
Distributed Application Development
Exception Handling in WCF Services
Dudy Fathan Ali, S.Kom (DFA)2017
CEP - CCITFakultas Teknik Universitas Indonesia
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Q8M1 – SC Dudy Fathan Ali S.Kom
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Objectives
Q8M1 – SC Dudy Fathan Ali S.Kom
Define Exception Handling
Implement Exception Handling
Q8M1 – SC Dudy Fathan Ali S.Kom
Define Exception Handling
Distributed Application Development
o Anticipating errors and providing error-handling code is known as exception handling.
o A WCF service and a client application communicate with each other by using SOAP.
o When an error occurs in the service, it needs to be communicated to the client in order to be handled properly.
Q8M1 – SC Dudy Fathan Ali S.Kom
Exception Communication by Using SOAP
Distributed Application Development
o When an unhandled exception occurs in a WCF service, a default exception is thrown and the communication between the service and the client application is discontinued.
o The exception thrown by a WCF service should be converted into the SOAP format so that any client can easily interpret it.
o The SOAP specification is used to convert the exception into a standard format.
o The SOAP specification provides a fault element that may be present in the body of the message sent by a WCF service to a client application.
Q8M1 – SC Dudy Fathan Ali S.Kom
Exception Communication by Using SOAP
Distributed Application Development
o The SOAP fault element is a standard format that contains the error message and information related to the error message.
o When WCF receives an unhandled exception at the service host, it faults the server channel and further communication between the clients and the service is halted.
Q8M1 – SC Dudy Fathan Ali S.Kom
Implementing Exception Handling
Distributed Application Development
o Exception handling is implemented to handle all the possible exceptions.
o To implement exception handling in a WCF service, you can use the following classes of the System.ServiceModel namespace:
o The FaultException class
o The generic FaultException class
Q8M1 – SC Dudy Fathan Ali S.Kom
Using the FaultException Class
Distributed Application Development
o The FaultException class is a base class that is used to handle exceptions in WCF.
o This class serializes the error messages that are thrown by a WCF service into the SOAP fault.
o The following code snippet shows the use of the FaultExceptionclass:
public int divideNumber(int num1, int num2)
{
if (num2 == 0)
{
throw new FaultException("Pembagi tidak boleh bernilai 0.");
}
int result = num1 / num2;
return result;
}
Q8M1 – SC Dudy Fathan Ali S.Kom
Using the FaultException Class
Distributed Application Development
o The following code snippet shows how a client application can access the exception class:
public void divideClient()
{
ServiceReference.ServiceClient obj;
obj = new ServiceReference.ServiceClient();
try
{
int result = obj.divideNumber(10, 0);
Console.WriteLine(result);
}
catch (FaultException faultEx)
{
Console.WriteLine(faultEx.Message);
}
}
Q8M1 – SC Dudy Fathan Ali S.Kom
Using the Generic FaultException Class
Distributed Application Development
o To enable a client application to access a user-defined class, you need to expose the class.
o To expose a user-defined exception class and send a customized message to a client application, you need to perform the following tasks:
o Define a user-defined exception class
o Define a FaultContract
o Throw a FaultException
Q8M1 – SC Dudy Fathan Ali S.Kom
Using the Generic FaultException Class
Distributed Application Development
o Define a user-defined exception class:
o While defining a user-defined exception class, you need to use the [DataContract] and [DataMember] attributes to expose the class and its members, as shown in the following code snippet:
[DataContract]
public class MyFaultException
{
[DataMember]
public string message;
}
Q8M1 – SC Dudy Fathan Ali S.Kom
Using the Generic FaultException Class
Distributed Application Development
o Define a [FaultContract]:
o The [FaultContract] attribute is defined to serialize the structure of the user-defined exception class.
o It indicates to a WCF service that a service’s WSDL should include the customized exception message sent to a client application.
Q8M1 – SC Dudy Fathan Ali S.Kom
Using the Generic FaultException Class
Distributed Application Development
o The following code snippet shows how to use the FaultContractattribute:
[ServiceContract]
public interface IService
{
[OperationContract]
[FaultContract(typeof(MyFaultException))]
int Divide(int numerator, int denominator);
}
[DataContract]
public class MyFaultException
{
[DataMember]
public string message;
}
Q8M1 – SC Dudy Fathan Ali S.Kom
Using the Generic FaultException Class
Distributed Application Development
o Throw a FaultException:
o To send a customized message in a SOAP fault format, you need to throw a FaultException exception that takes a user-defined class as a parameter.
Q8M1 – SC Dudy Fathan Ali S.Kom
Using the Generic FaultException Class
Distributed Application Development
o The following code snippet shows how to use the Generic FaultException class:
public int divideNumber(int num1, int num2)
{
if (num1 < num2)
{
MyFaultException objError = new MyFaultException();
objError.message = "Value of denominator can not be
greater than numerator";
throw new FaultException<MyFaultException>(objError);
}
int result = num1 / num2;
return result;
}
Q8M1 – SC Dudy Fathan Ali S.Kom
Using the Generic FaultException Class
Distributed Application Development
o The following code snippet shows how a client application can access the user-defined exception class:
public void divide()
{
ServiceRef.ServiceClient obj;
obj = new ServiceRef.ServiceClient();
try
{
int result = obj.divideNumber(10, 11);
Console.WriteLine(result);
}
catch (FaultException<ServiceRef.MyFaultException> faultEx)
{
Console.WriteLine(faultEx.Detail.message);
}
}
Q8M1 – SC Dudy Fathan Ali S.Kom
Thank You!Dudy Fathan Ali, S.Kom
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