Introduction to Behaviors - Page 1
       by kirupa  |  25 July 2009

Interactivity is all the rage these days. Everything has to do something interactive otherwise it is just not cool and worth using. Almost all applications you create or use these days contain some form of interactivity that goes beyond what you may have seen many years ago. When a timer hits a certain value, a movie starts to play. When you press down on your spacebar, a space ship fires a laser at a barrage of aliens. When you click on a button, you launch your browser to display a web page you specified:

[ image of Galaxian from Wikipedia ]

The fairly limited examples I showed in the previous paragraph are fairly diverse. Some are from video games, and some are from your standard run-of-the-mill applications that you use often. Despite their seeming variance, there is one thing they all share in commmon. In order to create the various components that make them up, you need to write code. If you are not someone very adept at writing code, implementing many forms of interactivity may simply be out of reach or very time consuming. To help address this problem, you have what are known as behaviors.

Introducing Behaviors
To paint with a broad brush, behaviors are reusable pieces of interactivity that you can easily add to your Silverlight or WPF applications using Expression Blend 3. As a user of behaviors, you can accomplish all of the tasks that I described above by just applying a behavior and tweaking a few properties. 

In this article, I am not going to delve into great detail on how you can write them. Instead, I am going to introduce behaviors by taking a non-trivial example and comparing the workflow for completing a task without using behaviors as well as completing a task using behaviors.

Setting the Stage
After seeing all the demos of Deep Zoom in Silverlight, you realized that you wanted to create your own little Silverlight application that used the Deep Zoom technology to display some photos. Here is an example of something created in Deep Zoom:

[ click/pan around the above example and use your mouse wheel to zoom ]

You launch Expression Blend, and In Blend, you draw out your MultiScaleImage control and point it to some Deep Zoom images you exported. The MultiScaleImage control is what you use to You test your application, and you see something that looks like the following in your browser:

[ everything looks OK... ]

So far so good. You then try playing with your application by performing some common Deep Zoom gestures such as clicking, sliding, and rolling your mousewheel just like you saw in my example. After a few seconds, you realize that all of your clicking, sliding, and mousewheeling isnít really doing anything to your Deep Zoom image. Nothing is happening! What is going on?

Here is what is going on. Out of the box, your MultiScaleImage control only provides you with the ability to view Deep Zoom content. Being able to interact with your content so that you can zoom and pan is something that you have to do on your own. This involves writing code...or does it? Find out on the next page.

Onwards to the next page!

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