ADO.NET 3.5 Cookbook, 2nd Edition

3.31. Querying Data Asynchronously with Message Queuing

Problem

You want to asynchronously retrieve data from a system that is not always connected.

Solution

You must:

• Use message queuing to construct and send a data request from the client.

• Access and process the requesting message at the server.

• Compose and send a response message containing the result set to the client.

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

The solution creates query and result message queues if they do not exist. A message is sent to the query queue containing the query. The message is retrieved from the message queue and the query is parsed from it. The query is processed and the results are sent to the result queue. Finally the message is received from the result queue, cast to a DataSet, and the result set is output to the console.

This project needs a reference to the System.Messaging assembly.

The C# code in Program.cs in the project AsynchronousQueryMSMQ is shown in Example 3-44.

Example 3-44. File: Program.cs for AsynchronousQueryMSMQ solution

using System; using System.Data; using System.Data.SqlClient; using System.Messaging; namespace AsynchronousQueryMSMQ { class Program { private static string queueNameQuery = @".\Private$\AdoNet35Cookbook_AsynchronousQuery"; private static string queueNameResult = @".\Private$\AdoNet35Cookbook_AsynchronousResult"; private static int contactID = 10; static void Main(string[] args) { // Create the query queue if it does not exist. if (!MessageQueue.Exists(queueNameQuery)) ...