Transactions provide a way to group a set of actions or operations into a single indivisible unit of execution. A transaction is a collection of operations with the following properties:

• Atomicity. This ensures that either all of the updates completed under a specific transaction are committed and made durable or they are all aborted and rolled back to their previous state.
  
  
• Consistency. This guarantees that the changes made under a transaction represent a transformation from one consistent state to another. For example, a transaction that transfers money from a checking account to a savings account does not change the amount of money in the overall bank account.
  
  
• Isolation. This prevents a transaction from observing uncommitted changes belonging to other concurrent transactions. Isolation provides an abstraction of concurrency while ensuring one transaction cannot have an unexpected impact on the execution of another transaction.
  
  
• Durability. This means that once committed, updates to managed resources (such as a database record) will be persistent in the face of failures.
  
  

Windows Communication Foundation (WCF) provides a rich set of features that enable you to create distributed transactions in your Web service application.

WCF implements support for the WS-AtomicTransaction (WS-AT) protocol that enables WCF applications to flow transactions to interoperable applications, such as interoperable Web services built using third-party technology. WCF also implements support for the OLE Transactions protocol, which can be used in scenarios where you do not need interop functionality to enable transaction flow.

You can use an application configuration file to configure bindings to enable or disable transaction flow, as well as set the desired transaction protocol on a binding. In addition, you can set transaction time-outs at the service level using the configuration file. For more information, see Enabling Transaction Flow.

Transaction attributes in the System.ServiceModel namespace allow you to do the following:

• Configure transaction time-outs and isolation-level filtering using the ServiceBehaviorAttribute attribute.
  
  
• Enable transactions functionality and configure transaction completion behavior using the OperationBehaviorAttribute attribute.
  
  
• Use the ServiceContractAttribute and OperationContractAttribute attributes on a contract method to require, allow or deny transaction flow.
  
  

For more information, see ServiceModel Transaction Attributes.

See Also