Simple Steps to Enable Transactions in WCF

Transaction is basically a logical unit of work comprising activities that all needed to be succeeded or failed, and also it must be compliant with ACID principals.

Movement of money from a bank account to another is a simple example of a transaction. In this single transaction, two operations will be performed. One account will be debited (amount will be taken from) and other will be credited (amount will be deposited).

Enabling transactions in Windows Communication Foundation is simple and straight forward but implementation sometimes becomes difficult depending upon the scenario. For example, implementing transactions in a distributed environment will definitely require effort and more things to consider.

Now, consider we already have developed a WCF service and we wanted to enable transactions on it. So, we will follow the steps below:

1. Add System.Transactions namespace to WCF Service project.
2. Set TransactionFlow property of the OperationContract attribute to Mandatory.

   Available options for TransactionFlow are:

   1. Mandatory - transaction must be flowed
   2. Allowed - transaction may be flowed
   3. Not Allowed - transaction is not flowed

   For example, our WCF service contract as follows:

   C#

   [TransactionFlow(TransactionFlowOptions.Mandatory]
   void MyMethod();

3. Now, set the OperationBehavior attribute for the implementing method.
   C#

   [OperationBehavior(TransactionScopeRequired=true, TransactionAutoComplete=true)]
   void MyMethod()
   {
   }

   TransactionScopeRequired = true means it can only be called in a transaction. TransactionAutoComplete = true means that if the operation completes successfully, transaction will be committed.

4. Enable Transactions for WCF Binding being used.

   For example, in our configuration file, bindings will be as follows:

   XML

   <bindings>
     <wsHttpBinding>
        <binding name="httpBinding"  transactionFlow="true"/>
     </ wsHttpBinding >
   </bindings>

   Remember that we must choose a binding that supports transactions, i.e., netTcpBinding, netNamedPipeBinding, wsHttpBinding, wsDualHttpBinding, and wsFederationHttpBinding.

5. Need to start the transaction from client as:
   C#

   using System.Transaction;
   Using( var transScope = new TransactionScope())
   {  
        //Calling service methods
        IMyServiceClient client = new IMyServiceClient();
        client.MyMethod();
        
        transScope.complete();    
   }

Optionally, if we wanted to specify the Isolation level for the transaction, we can add serviceBehavior attribute to implementing class as follows:

[ServiceBehavior(TransactionIsolationLevel=System.Transaction.IsolationLevel.Serializable)]
Public class MyService : IMyService{}

This is all we need to do for enabling transactions in WCF. There are few more things regarding "Service Instancing and Sessions" that need to be considered while working with Transactions but this WCF tutorial is more focused on enabling transactions in simple scenario. In my later WCF article on Windows Communication Foundation Transactions on this blog, I'll discuss those concepts in more details.

Other Top WCF Tutorials

• WCF - Top 10 Interview Questions
• WCF Vs ASMX Web Services
• Understanding WCF Bindings and Channel Stack
• Simple Steps to enable tracing in WCF