ADO.NET 3.5 Cookbook, 2nd Edition

5.15. Updating Data Asynchronously Using Message Queuing

Problem

You need to asynchronously update data in a database on a system that is not always connected.

Solution

Use message queuing and a XML DiffGrams to:

• Construct and send an MSMQ message containing a DiffGram to the server.

• Extract the DiffGram from the message and use it to update the data source at the server.

• Construct and send a message containing the latest DataSet to the client.

• Retrieve the response at the client and deserialize it into a DataSet.

The solution performs the following steps:

• Creates three message queues, if they do not already exist—one each for the query command (AdoNet35Cookbook_queueNameUpdateQuery), the query results (AdoNet35Cookbook_queueNameUpdateResult), and the update command (AdoNet35Cookbook_AsynchronousUpdateCommand). In this example, the query and update commands are issued from the same computer that processes the query and update—in a real situation, these tasks would be processed on different computers that might not always be connected.

• Creates a query message and sends it to the query command queue.

• Gets and deserializes the query message from the query command queue, creates and executes the query, and sends the result set to the result queue.

• Gets the result set from the result queue and creates the result DataSet by deserializing the message body.

• Outputs the result set in the DataSet to the console.

• Updates the row in the first (only) DataSet table with Id = 2.

• Creates a DiffGram containing ...