Question

What is exception handling? How is exception handling in web applications and services different? What are the different options available in ASP.NET to trace, track, and handle run time errors?

Answer 1

Answer:

1)

Exceptions are a type of error that occurs during the execution of an application. Errors are typically problems that are not expected. Whereas, exceptions are expected to happen within the application’s code for various reasons.

Applications use exception handling logic to explicitly handle the exceptions when they happen. Exceptions can occur for a wide variety of reasons. From the infamous NullReferenceException to a database query timeout.

Exceptions allow an application to transfer control from one part of the code to another. When an exception is thrown, the current flow of the code is interrupted and handed back to a parent try catch block. C# exception handling is done with the follow keywords: try, catch, finally, and throw

• try – A try block is used to encapsulate a region of code. If any code throws an exception within that try block, the exception will be handled by the corresponding catch.
• catch – When an exception occurs, the Catch block of code is executed. This is where you are able to handle the exception, log it, or ignore it.
• finally – The finally block allows you to execute certain code if an exception is thrown or not. For example, disposing of an object that must be disposed of.
• throw – The throw keyword is used to actually create a new exception that is the bubbled up to a try catch finally block.

Exception Handling in Web Services

Web Services are a relatively new way to achieve distributed computing. In distributed computing, applications are designed as services that run on a server. Clients access these services through a programmable interface. When there is an exception during the execution of the Web service, the Web service should not only capture the exceptions, but also communicate the exception back to the consumers of the Web service. Because Web services provide a platform-independent of way of leveraging a specific functionality, the exceptions that occur in the Web Services must also be communicated in a platform-independent manner. To accomplish this, you need to make sure that the exceptions raised from the Web services are compliant with the SOAP specification. In this article, we will understand how to raise exceptions from a Web service by using the SoapException object that provides an industry-standard way of representing a SOAP Fault. We will also see how to handle this exception from the Web service consumer application

Handling exceptions in a Web service is no different than handling exceptions in a Web or Windows application. However, when designing exception blocks in Web services, you need to be aware of the fact that you need to communicate the exception information to the consumers of your Web service in a platform-independent manner based on the SOAP specification. To accomplish this, you should use the SoapException class that abstracts the complexities of the SOAP fault creation process. The SoapException class consists of the following properties that need to be populated before throwing the exception to the consumers.

• Message—Contents of the exception
• Code—Enum constant that specifies the type of Fault code (e.g. ClientFaultCode, ServerFaultCode)
• Actor—URL of the Web service method where the exception has occurred
• Detail—Detail element can be used to communicate more information about the exception to the callers