Approaches to data synchronization on windows mobile

The growing capabilities of mobile devices such as the Pocket PC, and their increasingly

widespread usage within the commercial world, provide an opportunity for business

solutions to broaden their spread to include remote and mobile workers. All of these may require access to the corporate IT system - in either a connected or a disconnected scenario, and data synchronization between a mobile device and the server is an essential component of such systems.

This blog entry (in two parts ) explains in brief two approaches to tackle the data synchronization problem:

1. Disconnected web services (using Disconnected Service Agent from Mobile Client Software Factory)

2. Sql Server Merge Replication over Http.

1. Disconnected Web services

In this method, we make use of the Disconnected Service Agent Application Block provided by the Mobile Client Software Factory (which can be downloaded from). The Disconnected Service Agent Block (DSAB) provides features for storing offline Web Service requests, and executing them when connectivity is available

There are two distinct sections in the Disconnected Service Agent Block:

1. A subsystem that allows developers to invoke disconnected Web Services. The Service Agent queues requests and keeps track of the asynchronous callbacks that the application expects to receive when the Web Service responds.

2. A Dispatcher that determines exactly when to dispatch each call to a Web

Service, depending on connectivity conditions, pricing policies, and configuration

settings. When the correct conditions occur, the dispatcher makes the request,

using the appropriate credentials and addresses for the endpoint.

The Disconnected Service Agent Block exposes several core classes that you work

with when using the services provided by this block:

• The RequestManager class implements and manages the request queues, and

uses the services of the WebServiceRequestDispatcher class to dispatch these

requests. It stores the queues of pending and failed requests in the SQL Server

Mobile Edition database on the device using the DatabaseRequestQueue class,

or a custom implementation of the IRequestQueue interface.

• The Request class provides facilities for creating Web Service requests, adding

the arguments or parameters required by the Web Service method, specifying

the endpoint for delivery of the request, and setting the properties for handling

and delivery of the request.

• The ConnectionMonitorAdapter class provides information about the

connection used by the request, such as the price and network details, and

raises events when status of the connection changes. It sits between the RequestManager and theConnectionMonitor, acting as broker for request and the events raised by ConnectionMonitor.