Transacted MSMQ Binding
This sample demonstrates how to perform transacted queued communication by using Message Queuing (MSMQ).
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The setup procedure and build instructions for this sample are located at the end of this topic. |
In queued communication, the client communicates to the service using a queue. More precisely, the client sends messages to a queue. The service receives messages from the queue. The service and client, therefore, do not have to be running at the same time to communicate using a queue.
When transactions are used to send and receive messages, there are actually two separate transactions. When the client sends messages within the scope of a transaction, the transaction is local to the client and the client queue manager. When the service receives messages within the scope of the transaction, the transaction is local to the service and the receiving queue manager. It is very important to remember that the client and the service are not participating in the same transaction; rather, they are using different transactions when performing their operations (such as send and receive) with the queue.
In this sample, the client sends a batch of messages to the service from within the scope of a transaction. The messages sent to the queue are then received by the service within the transaction scope defined by the service.
The service contract is IOrderProcessor, as shown in the following sample code. The interface defines a one-way service that is suitable for use with queues:
[ServiceContract(Namespace="http://Microsoft.ServiceModel.Samples")]
public interface IOrderProcessor
{
[OperationContract(IsOneWay = true)]
void SubmitPurchaseOrder(PurchaseOrder po);
}
The service behavior defines an operation behavior with TransactionScopeRequired set to true. This ensures that the same transaction scope that is used to retrieve the message from the queue is used by any resource managers accessed by the method. It also guarantees that if the method throws an exception, the message is returned to the queue. Without setting this operation behavior, a queued channel creates a transaction to read the message from the queue and commits it automatically before dispatch such that if the operation fails, the message is lost. The most common scenario is for service operations to enlist in the transaction that is used to read the message from the queue, as demonstrated in the following code:
// This service class that implements the service contract.
// This added code writes output to the console window.
public class OrderProcessorService : IOrderProcessor
{
[OperationBehavior(TransactionScopeRequired = true, TransactionAutoComplete = true)]
public void SubmitPurchaseOrder(PurchaseOrder po)
{
Orders.Add(po);
Console.WriteLine("Processing {0} ", po);
}
…
}
The service is self hosted. When using the MSMQ transport, the queue used must be created in advance. This can be done manually or through code. In this sample, the service contains code to check for the existence of the queue and create the queue if it does not exist. The queue name is read from the configuration file. The base address is used by the Service Model Metadata Utility Tool (Svcutil.exe) to generate the proxy to the service:
// Host the service within this EXE console application.
public static void Main()
{
// Get the MSMQ queue name from appSettings in configuration.
string queueName = ConfigurationManager.AppSettings["queueName"];
// Create the transacted MSMQ queue if necessary.
if (!MessageQueue.Exists(queueName))
MessageQueue.Create(queueName, true);
// Create a ServiceHost for the OrderProcessorService type.
using (ServiceHost serviceHost = new ServiceHost(typeof(OrderProcessorService)))
{
// Open the ServiceHost to create listeners and start listening for messages.
serviceHost.Open();
// The service can now be accessed.
Console.WriteLine("The service is ready.");
Console.WriteLine("Press <ENTER> to terminate service.");
Console.WriteLine();
Console.ReadLine();
// Close the ServiceHost to shut down the service.
serviceHost.Close();
}
}
The MSMQ queue name is specified in an appSettings section of the configuration file, as shown in the following sample configuration:
<appSettings>
<add key="queueName" value=".\private$\ServiceModelSamplesTransacted" />
</appSettings>
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The queue name uses a dot (.) for the local machine and backslash separators in its path when creating the queue using System.Messaging. The Windows Communication Foundation (WCF) endpoint uses the queue address with net.msmq scheme, uses "localhost" to denote the local machine, and uses forward slashes in its path. |
The client creates a transaction scope. Communication with the queue takes place within the scope of the transaction, causing it to be treated as an atomic unit where all messages are sent to the queue or none of the messages are sent to the queue. The transaction is committed by calling Complete on the transaction scope:
// Create a client.
OrderProcessorClient client = new OrderProcessorClient();
// Create the purchase order.
PurchaseOrder po = new PurchaseOrder();
po.CustomerId = "somecustomer.com";
po.PONumber = Guid.NewGuid().ToString();
PurchaseOrderLineItem lineItem1 = new PurchaseOrderLineItem();
lineItem1.ProductId = "Blue Widget";
lineItem1.Quantity = 54;
lineItem1.UnitCost = 29.99F;
PurchaseOrderLineItem lineItem2 = new PurchaseOrderLineItem();
lineItem2.ProductId = "Red Widget";
lineItem2.Quantity = 890;
lineItem2.UnitCost = 45.89F;
po.orderLineItems = new PurchaseOrderLineItem[2];
po.orderLineItems[0] = lineItem1;
po.orderLineItems[1] = lineItem2;
// Create a transaction scope.
using (TransactionScope scope = new TransactionScope(TransactionScopeOption.Required))
{
// Make a queued call to submit the purchase order.
client.SubmitPurchaseOrder(po);
// Complete the transaction.
scope.Complete();
}
// Closing the client gracefully closes the connection and cleans up resources.
client.Close();
Console.WriteLine();
Console.WriteLine("Press <ENTER> to terminate client.");
Console.ReadLine();
To verify that transactions are working, modify the client by commenting the transaction scope as shown in the following sample code, rebuild the solution, and run the client:
//scope.Complete();
Because the transaction is not completed, the messages are not sent to the queue.
When you run the sample, the client and service activities are displayed in both the service and client console windows. You can see the service receive messages from the client. Press ENTER in each console window to shut down the service and client. Note that because queuing is in use, the client and service do not have to be up and running at the same time. You can run the client, shut it down, and then start up the service and it still receives the messages.
The service is ready.
Press <ENTER> to terminate service.
Processing Purchase Order: 7b31ce51-ae7c-4def-9b8b-617e4288eafd
Customer: somecustomer.com
OrderDetails
Order LineItem: 54 of Blue Widget @unit price: $29.99
Order LineItem: 890 of Red Widget @unit price: $45.89
Total cost of this order: $42461.56
Order status: Pending
To set up, build, and run the sample
Ensure that you have performed the One-Time Setup Procedure for the Windows Communication Foundation Samples.
To build the C# or Visual Basic .NET edition of the solution, follow the instructions in Building the Windows Communication Foundation Samples.
To run the sample in a single- or cross-machine configuration, follow the instructions in Running the Windows Communication Foundation Samples.
By default with the NetMsmqBinding, transport security is enabled. There are two relevant properties for MSMQ transport security, MsmqAuthenticationMode and MsmqProtectionLevel. By default, the authentication mode is set to Windows and the protection level is set to Sign. For MSMQ to provide the authentication and signing feature, it must be part of a domain and the Active Directory integration option for MSMQ must be installed. If you run this sample on a computer that does not satisfy these criteria, you receive an error.
To run the sample on a computer joined to a workgroup or without Active Directory integration
If your computer is not part of a domain or does not have Active Directory integration installed, turn off transport security by setting the authentication mode and protection level to None as shown in the following sample configuration code:
<system.serviceModel> <services> <service name="Microsoft.ServiceModel.Samples.OrderProcessorService" behaviorConfiguration="OrderProcessorServiceBehavior"> <host> <baseAddresses> <add baseAddress="https://localhost:8000/ServiceModelSamples/service"/> </baseAddresses> </host> <!-- Define NetMsmqEndpoint. --> <endpoint address="net.msmq://localhost/private/ServiceModelSamplesTransacted" binding="netMsmqBinding" bindingConfiguration="Binding1" contract="Microsoft.ServiceModel.Samples.IOrderProcessor" /> <!-- The mex endpoint is explosed at https://localhost:8000/ServiceModelSamples/service/mex. --> <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" /> </service> </services> <bindings> <netMsmqBinding> <binding name="Binding1"> <security mode="None" /> </binding> </netMsmqBinding> </bindings> <behaviors> <serviceBehaviors> <behavior name="OrderProcessorServiceBehavior"> <serviceMetadata httpGetEnabled="True"/> </behavior> </serviceBehaviors> </behaviors> </system.serviceModel>Ensure that you change the configuration on both the server and the client before you run the sample.
Note:Setting securitymode to None is equivalent to setting MsmqAuthenticationMode, MsmqProtectionLevel, and Message security to None.
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