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:
- Add
System.Transactions
namespace to WCF Service project. - Set
TransactionFlow
property of the OperationContract
attribute to Mandatory
.
Available options for TransactionFlow
are:
- Mandatory - transaction must be flowed
- Allowed - transaction may be flowed
- Not Allowed - transaction is not flowed
For example, our WCF service contract as follows:
[TransactionFlow(TransactionFlowOptions.Mandatory]
void MyMethod();
- Now, set the
OperationBehavior
attribute for the implementing method.
[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.
- Enable Transactions for WCF Binding being used.
For example, in our configuration file, bindings will be as follows:
<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
.
- Need to start the transaction from client as:
using System.Transaction;
Using( var transScope = new TransactionScope())
{
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.
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