Parsing Addresses and More with the MapPoint Web Service Find APIs - AJAX-Enabling Your Web Applications (Page 2 of 5 )
In theory, AJAX is no different from any other web application that uses HTTP request and response—however, adding asynchronous calls from your web page to the web server that uses JavaScript dramatically improves the user’s experience.
To understand how to leverage AJAX in your MapPoint Web Service web applications, you need to understand how AJAX works, which is explained in the following section.
For AJAX to work, you need three core components:
- A web page (htm, aspx, etc.) that hosts JavaScript containing asynchronous calls to the web server
- XMLHTTP ActiveX control enabled from the client web browser
- A server-side component that can process HTTP GET requests using the query string parameters
All three of these components together make an AJAX implementation. Usually, the server-side component is an HTTP Handler, since it renders only the script instead of conventional HTML. An HTTP Handler is similar to an ISAPI extension, and you need to implement the IHTTPHandler interface to develop an ASP.NET HTTP Handler. These concepts are shown pictorially in Figure 6-3.
Since designing a web page and writing JavaScript are straightforward tasks, let me delve into the server-side components that are required for AJAX.
For example, you want to develop a web application that implements “Find a place” functionality; in this application, when users search for a place, generally MapPoint Web Service comes back with a list of possible matches to be displayed for disambiguation. Conventionally, you would implement this process using the following series of actions:
Figure 6-3. AJAX architecture for MapPoint Web Service applications
- Have the user type in a place and click a button to find it.
- Post the request to the server page that invokes the MapPoint Find Service calls to find the place.
- If there is more than one match to the input string, display them in a list box where the user can select the place that he is looking for.
- Post that selection back to the server page that invokes MapPoint Render Service to get a map.
The same application can be implemented with AJAX to improve the overall user experience:
- As the user types each character into the input place textbox, make an asynchronous call to the server to fetch matching places and display them in a dynamic drop-down list.
- Have the user select the place she is looking for.
- Post that selection back to the server page to display a map.
An implementation of this application results in the user interface shown in Figure 6-4.
The experience of using the application is far richer with AJAX when compared to a traditional MapPoint find web application. Next, let’s see how to implement this application.
Figure 6-4. Place lookup using MapPoint Web Service and AJAX
Next: Implementing MapPoint Lookup AJAX Application >>
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 This article is excerpted from chapter six of the book Programming MapPoint in .NET, written by Chandu Thota (O'Reilly; ISBN: 0596009062). Check it out today at your favorite bookstore. Buy this book now.
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