Many enterprise applications today require reliable message delivery mechanism. This is absolutely essential in financial transactions. There are a number of techniques available to achieve this including a Custom made Queuing server, the underlying protocol in that case would be Transfer Control Protocol TCP and it has to be made reliable by wrapping it in a layer of requests and acknowledgements, persisting all the requests and acknowledgements of a transaction in a database and applying rules for “Transaction Processing” as in a database. So the transaction is literally atomic and has many phases.This is sometimes difficult to achieve since implementing Sockets is itself a difficult proposition, it comes with the issues of Server client synchronization , memory management with multiple threads and usually the proprietary protocol that’s used for message passing or a custom developed API which needs to be configured for server and clients.
I have recently used MSMQ and was able to achieve all this without the need to develop long API or a lot of development. Integrating it with C# was very easy and the message passing has been very reliable. All the threads, queue management and connection are in built into MSMQ .In this article I would describe the basic things that you need to do to integrate MSMQ into your projects. Before using any of the sample code makes sure that MSMQ is installed on your system. If not it can be installed from the Add/Remove Windows component option. Once it is installed it is displayed in the administrative applications list and then you can use the code similar to one described in various sections. Make sure you add following references in your application:
Writing Strings or Formatted Objects to MSMQ:
The sample code below would create a Message Queue in the private queues list with the name TestMSMQ. All messages that you post would be posted in this queue. // Name of the Private Queu you want to post data to
String queueName = “.\private$\TestMSMQ”; // The string message tou want to send// The objects of user defined classes can also be sent
// MSMQ holds the serizlized version when received the body // should be converted to the same class object againString messageToSend = “This is a test message”; // the message object that would be send
System.Object obj = messageToSend; // Create a MSMQ message queuing transaction.
MessageQueueTransaction msgTran = new MessageQueueTransaction(); // Begin a MSMQ transaction.// If the Queue doesn’t exist create it Using API
msgTran.Begin(); if (MessageQueue.Exists(queueName))
msgQueue = new MessageQueue(queueName);
msgQueue = MessageQueue.Create(queueName);
msgQueue = new MessageQueue(queueName);
Message msg = new Message(); // Assign the message to the BODY Property
msg.Body = obj; // Associate a binary or an XML formatter
msg.Formatter = new System.Messaging.BinaryMessageFormatter(); // Send the Message
msgQueue.Send(msg, msgTr); // Commit the transaction.
msgTran.Commit(); Reading from MSMQ:
Receiving a Message from the Message Queue is Simple. If a user defined datatype resides in the body of the message and the Message queue is accessed from different applciations, services the same type should exist in both the services , applications. This can be done by placing them in a project and adding a reference to the project in both the applications , then converting the object returned by the Body of the message to an instance of the required Type. Note:Receiving a message would dequeue the Message from MessageQueue. If you want to make sure that whenever a message is removed from the message queue a copy of it is saved you can use the Journal queue by setting the use journal queue flag while posting to the message queue. However if you don’t want to dequeue the message an Enumerator can be obtained and be processed with a loop that peeks the Message Queue messages. Use Peek instead of Receive and Receive only when absolutely certain about removing the message from the queue. // process the online messages here
string onlineQueueName = .\private$\TestMSMQ”; // initialize the Message Queue instance
MessageQueue msgQueue;msgQueue = new MessageQueue(onlineQueueName); System.Messaging.Message Msg = null; Msg = olMq.Receive();Note : If you might be interested in working code for MSMQ or have some design and architecture ideas feel free to discuss or email me at firstname.lastname@example.org