Flowing Transactions into and out of Workflow Services

Article
03/02/2012

This topic applies to Windows Workflow Foundation 4 (WF4).

Workflow services and clients can participate in transactions. For a service operation to become part of an ambient transaction, place a Receive activity within a TransactedReceiveScope activity. Any calls made by a Send or a SendReply activity within the TransactedReceiveScope will also be made within the ambient transaction. A workflow client application can create an ambient transaction by using the TransactionScope activity and call service operations using the ambient transaction. This topic walks you through creating a workflow service and workflow client that participate in transactions.

Caution:
If a workflow service instance is loaded within a transaction and the workflow contains a Persist activity, the workflow instance will hang until the transaction times out.

Note:
Whenever you use a TransactedReceiveScope it is recommended to place all Receives in the workflow within TransactedReceiveScope activities.

Note:
When using TransactedReceiveScope and messages arrive in the incorrect order, the workflow will be aborted when trying to deliver the first out of order message. You must make sure your workflow is always at a consistent stopping point when the workflow idles. This will allow you to restart the workflow from a previous persistence point should the workflow be aborted.

Create a shared library

Create a new empty Visual Studio Solution.
Add a new class library project called Common. Add references to the following assemblies:
- System.Activities.dll
- System.ServiceModel.dll
- System.ServiceModel.Activities.dll
- System.Transactions.dll

Add a new class called PrintTransactionInfo to the Common project. This class is derived from NativeActivity and overloads the Execute method.

using System;
using System;
using System.Activities;
using System.Transactions;

namespace Common
{
    public class PrintTransactionInfo : NativeActivity
    {
        protected override void Execute(NativeActivityContext context)
        {
            RuntimeTransactionHandle rth = context.Properties.Find(typeof(RuntimeTransactionHandle).FullName) as RuntimeTransactionHandle;

            if (rth == null)
            {
                Console.WriteLine("There is no ambient RuntimeTransactionHandle");
            }

            Transaction t = rth.GetCurrentTransaction(context);

            if (t == null)
            {
                Console.WriteLine("There is no ambient transaction");
            }
            else
            {
                Console.WriteLine("Transaction: {0} is {1}", t.TransactionInformation.DistributedIdentifier, t.TransactionInformation.Status);
            }
        }
    }

}

This is a native activity that displays information about the ambient transaction and is used in both the service and client workflows used in this topic. Build the solution to make this activity available in the Common section of the Toolbox.

Implement the workflow service

Add a new WCF Workflow Service, called ServiceWorkflow to the Common project. To do this right click the Common project, select Add, New Item ..., Select Workflow under Installed Templates and select WCF Workflow Service.
Delete the default ReceiveRequest and SendResponse activities.
Drag and drop a WriteLine activity into the Sequential Service activity. Set the text property to "Workflow Service starting ..." as shown in the following example.
Drag and drop a TransactedReceiveScope after the WriteLine activity. The TransactedReceiveScope activity can be found in the Messaging section of the Toolbox. The TransactedReceiveScope activity is composed of two sections Request and Body. The Request section contains the Receive activity. The Body section contains the activities to execute within a transaction after a message has been received.
Select the TransactedReceiveScope activity and click the Variables button. Add the following variables.

Note

You can delete the data variable that is there by default. You can also use the existing handle variable.
Drag and drop a Receive activity within the Request section of the TransactedReceiveScope activity. Set the following properties:

Property Value

CanCreateInstance

True (check the checkbox)

OperationName

StartSample

ServiceContractName

ITransactionSample

The workflow should look like this:
Click the Define... link in the Receive activity and make the following settings:
Drag and drop a Sequence activity into the Body section of the TransactedReceiveScope. Within the Sequence activity drag and drop two WriteLine activities and set the Text properties as shown in the following table.

Activity Value

1st WriteLine

“Service: Receive Completed”

2nd WriteLine

"Service: Received = " + requestMessage

The workflow should now look like this:
Drag and drop the PrintTransactionInfo activity after the second WriteLine activity in the Body in the TransactedReceiveScope activity.
Drag and drop an Assign activity after the PrintTransactionInfo activity and set its properties according to the following table.

Property Value

To

replyMessage

Value

"Service: Sending reply."
Drag and drop a WriteLine activity after the Assign activity and set its Text property to "Service: Begin reply."

The workflow should now look like this:
Right click the Receive activity and select Create SendReply and paste it after the last WriteLine activity. Click the Define... link in the SendReplyToReceive activity and make the following settings.
Drag and drop a WriteLine activity after the SendReplyToReceive activity and set it’s Text property to "Service: Reply sent.”
Drag and drop a WriteLine activity at the bottom of the workflow and set its Text property to "Service: Workflow ends, press ENTER to exit."

The completed service workflow should look like this:

Property	Value
CanCreateInstance	True (check the checkbox)
OperationName	StartSample
ServiceContractName	ITransactionSample

Activity	Value
1st WriteLine	“Service: Receive Completed”
2nd WriteLine	"Service: Received = " + requestMessage

Property	Value
To	replyMessage
Value	"Service: Sending reply."

Implement the workflow client

Add a new WCF Workflow application, called ClientWorkflow to the Common project. To do this right click the Common project, select Add, New Item ..., Select Workflow under Installed Templates and select Activity.
Drag and drop a Sequence activity onto the design surface.
Within the Sequence activity drag and drop a WriteLine activity and set its Text property to "Client: Workflow starting". The workflow should now look like this:
Drag and drop a TransactionScope activity after the WriteLine activity. Select the TransactionScope activity, click the Variables button and add the following variables.
Drag and drop a Sequence activity into the body of the TransactionScope activity.
Drag and drop a PrintTransactionInfo activity within the Sequence
Drag and drop a WriteLine activity after the PrintTransactionInfo activity and set its Text property to “Client: Beginning Send”. The workflow should now look like this:
Drag and drop a Send activity after the Assign activity and set the following properties:

Property Value

EndpointConfigurationName

workflowServiceEndpoint

OperationName

StartSample

ServiceContractName

ITransactionSample

The workflow should now look like this:
Click the Define... link and make the following settings:
Right click the Send activity and select Create ReceiveReply. The ReceiveReply activity will be automatically placed after the Send activity.
Click the Define... link on the ReceiveReplyForSend activity and make the following settings:
Drag and drop a WriteLine activity between the Send and ReceiveReply activities and set its Text property to "Client: Send complete."
Drag and drop a WriteLine activity after the ReceiveReply activity and set its Text property to "Client side: Reply received = " + replyMessage
Drag and drop a PrintTransactionInfo activity after the WriteLine activity.
Drag and drop a WriteLine activity at the end of the workflow and set its Text property to "Client workflow ends." The completed client workflow should look like the following diagram.
Build the solution.

Property	Value
EndpointConfigurationName	workflowServiceEndpoint
OperationName	StartSample
ServiceContractName	ITransactionSample

Create the Service application

Add a new Console Application project called Service to the solution. Add references to the following assemblies:
1. System.Activities.dll
2. System.ServiceModel.dll
3. System.ServiceModel.Activities.dll

Open the generated Program.cs file and the following code:

  static void Main()
        {
            Console.WriteLine("Building the server.");
            using (WorkflowServiceHost host = new WorkflowServiceHost(new DeclarativeServiceWorkflow(), new Uri("net.tcp://localhost:8000/TransactedReceiveService/Declarative")))
            {              
                //Start the server
                host.Open();
                Console.WriteLine("Service started.");

                Console.WriteLine();
                Console.ReadLine();
                //Shutdown
                host.Close();
            };       
        }

Add the following app.config file to the project.

<?xml version="1.0" encoding="utf-8" ?>
<!-- Copyright © Microsoft Corporation.  All rights reserved. -->
<configuration>
    <system.serviceModel>
        <bindings>
            <netTcpBinding>
                <binding transactionFlow="true" />
            </netTcpBinding>
        </bindings>
    </system.serviceModel>
</configuration>

Create the client application

Add a new Console Application project called Client to the solution. Add a reference to System.Activities.dll.

Open the program.cs file and add the following code.

class Program
    {

        private static AutoResetEvent syncEvent = new AutoResetEvent(false);

        static void Main(string[] args)
        {
            //Build client
            Console.WriteLine("Building the client.");
            WorkflowApplication client = new WorkflowApplication(new DeclarativeClientWorkflow());
            client.Completed = Program.Completed;
            client.Aborted = Program.Aborted;
            client.OnUnhandledException = Program.OnUnhandledException;

            //Wait for service to start
            Console.WriteLine("Press ENTER once service is started.");
            Console.ReadLine();

            //Start the client            
            Console.WriteLine("Starting the client.");
            client.Run();
            syncEvent.WaitOne();

            //Sample complete
            Console.WriteLine();
            Console.WriteLine("Client complete. Press ENTER to exit.");
            Console.ReadLine();
        }

        private static void Completed(WorkflowApplicationCompletedEventArgs e)
        {
            Program.syncEvent.Set();
        }

        private static void Aborted(WorkflowApplicationAbortedEventArgs e)
        {
            Console.WriteLine("Client Aborted: {0}", e.Reason);
            Program.syncEvent.Set();
        }

        private static UnhandledExceptionAction OnUnhandledException(WorkflowApplicationUnhandledExceptionEventArgs e)
        {
            Console.WriteLine("Client had an unhandled exception: {0}", e.UnhandledException);
            return UnhandledExceptionAction.Cancel;
        }
    }

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Flowing Transactions into and out of Workflow Services

Create a shared library

Implement the workflow service

Implement the workflow client

Create the Service application

Create the client application

See Also

Tasks

Other Resources

Additional resources