This sample demonstrates how to compensate the transaction that has already been committed in the orchestration using the following sequence of steps:

1. Enter the customer data in the InfoPath form and submit the data to an orchestration that has been exposed as a Web service.
   
   
2. The orchestration has two parallel actions. One returns an acknowledgment to the InfoPath form and the other updates the Northwind and BTSCompensationSampleMailingList databases.
   
   
3. In the second action, the orchestration maps the incoming message to a customer relationship management (CRM) application message format and then updates the Customers table in the Northwind database. After this, the Mailing List table in the BTSCompensationSampleMailingList database is updated.
   
   
4. If either update fails, the changes made to the Northwind database are compensated by calling an external assembly to write the original customer data back to the database.
   
   

A Scope shape is primarily used for transactional execution and exception handling, including compensation. A scope consists of two blocks. The first block is the context block and the second block can be one or more exception-handling or compensation blocks. This is similar to the try-catch statement in the .NET programming language. In the UpdateContact.odx orchestration, there are two parallel actions. At the right-side branch, the try block is the Scope shape named Updated Backend Systems, which has a Long-Running transaction type and an Upd_Backend transaction identifier. Further down in the flow, there is a catch block that catches the general exception and initiates the compensation.

For more information about the Scope shape, see Scopes. Also see How to Configure the Scope Shape.

Note
The orchestration must itself be a long-running transaction for you to set the transaction type to Atomic or Long-Running.

In the try block, there are two scopes named Update CRM and Update Mailing. Both of these scopes are atomic transactions. In the Update CRM scope, there is a try block and a compensation block. The try block updates the Northwind database through a method call to an external assembly. The compensation block is where the compensation action takes place. When an exception happens in the Update Backend Systems scope, the code in Undo CRM Expression Shape updates the record back to its original state. This is triggered by the Compensate shape in the Catch Exception block.

Note
Atomic transactions guarantee that any partial updates are rolled back automatically in the event of a failure during the transactional update, and that the effects of the transaction are erased (except for the effects of any .NET calls that are made in the transaction).

Note
A long-running transaction is considered committed when the last statement in it has completed. There is no automatic rollback of state in case of a transaction abort. You can achieve this programmatically through the exception and compensation handlers demonstrated in this sample.

In the catch block, there is one Delay shape set for ten seconds. This delays the compensation action. There is also a Compensate shape that initiates the compensation action in the Upd_Backend transaction.

The following happens after the orchestration receives the input message:

1. The UpdateCrm assembly updates a row in the Northwind database.
   
   
2. The UpdateMailingList assembly updates a matching record in the BTSCompensationSampleMailingList database.
   
   
3. In the event of a failure while updating the Northwind database, an exception is raised and the orchestration exits the process.
   
   
4. In the event of a failure while updating the BTSCompensationSampleMailingList database, an exception is raised and a ten-second delay takes place before rewriting the original customer data back to the Northwind database.
   
   

<Samples Path>\Orchestrations\Compensation\

The following table shows the files in this sample and describes their purpose.

After you build and initialize this sample, consider the following before you run it:

• If you are running this sample against SQL Server 2005 or SQL Server 2008, you need to download the Northwind sample database first. You can download it from http://go.microsoft.com/fwlink/?LinkId=62009.
  
  
• Follow the instructions in the Readme file to install the Northwind database on SQL Server 2005 or SQL Server 2008.
  
  
• If you are running this sample on Windows Server 2003 or Windows Server 2008, you must create an IIS application pool and set its identity to an account that is a member of the BizTalk Application Users Windows group. You also need to update the orchestration Web service virtual directory to run within this application pool.
  
  
• Add the ASPNET account to the BizTalk Isolated Host Users group.
  
  
• Give the BizTalk Application Users group db_owner permission to the BTSCompensationSampleMailingList and Northwind databases.
  
  
• If BizTalk Server is not installed in the default location drive:\Program Files\Microsoft BizTalk Server 2009\, you must publish the Contact Info Update.xsn form before using it. To do so, do the following:
  
  
   To publish the InfoPath form

  1. In Internet Explorer, on the Tools menu, click Internet Options.

  2. On the Security tab, click Internet, and then click Custom Level.

  3. In the Miscellaneous section, ensure that the Access data sources across domains setting is enabled, and then click OK. This setting is required for the InfoPath user interface solution scripting code to run.

  4. In Windows Explorer, navigate to <Samples Path>\Orchestrations\Compensation\InfoPath, right-click Contact Info Update.xsn and then click Design.

  5. The InfoPath Contact Info Update solution opens in design mode.

  6. In the InfoPath Contact Info Update application, on the File menu, click Publish.

  7. The Publish Wizard appears.

  8. Select To a shared folder on this computer or on a network and publish the solution to the path <Samples Path>\Orchestrations\Compensation\InfoPath\Contact Info Update.xsn.

  9. Close the design mode InfoPath.

• You are ready to run this sample.
  
  
   To run the Compensation sample

  1. Double-click Contact Info Update.xsn to open it in InfoPath.

  2. Fill out the form for an account that exists in both databases. For example, use an existing account ID "ALFKI" from the Northwind Customers table.

  3. On the File menu, select Submit and click Submit.

  4. The response document should appear in the <Samples Path>\Orchestrations\Compensation\Out folder, and both the Northwind and the BTSCompensationSampleMailingList databases should be updated with the new data from the InfoPath form.

     Note

     You can detach the BTSCompensationSampleMailingList database or take it offline to test the compensation action that the orchestration performs. Observe that the record is updated in the Northwind database first. Then, when the orchestration tries to update the BTSCompensationSampleMailingList database, because that database is detached, the update fails. Therefore, an exception is raised and there is a ten-second delay before the compensation action takes place to write the original customer data back to the Northwind database.

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