I would encourage everyone who works with Silverlight to take a good hard look at Behaviors.  A Behavior is basically some code-behind logic that operates on Silverlight UI elements, bundled into a nice little package that can be in Xaml.  Behaviors can support parameters as well, making them both flexible and extensible.  In Expression Blend 3, several behaviors are provided out-of-the-box.  There is a drag/drop behavior, and a behavior that allows you to control storyboard animations based on events, just to name a couple. 

Below is a Silverlight example of a Rectangle that uses these two behaviors.  When the mouse enters the rectangle, it will alternate colors between red and yellow.  You can also drag the rectangle around.  Check it out…

And here is the Xaml representation of the above Silverlight application:

As you can see this is about 30 lines of Xaml that I was able to produce with simple point and click in Expression Blend.  Notice the elements that start with <i:…/>  These are the behaviors that control the storyboard and mouse drag.

The beauty of Behaviors is that they are so easy to use and are highly reusable.  They can also be quite powerful when combined together to create complex user interactions.

I question came up over at silverlight.net that I wrote an example for.  The scenario is that we want to bind our RIA Service data context to a DataGrid control via a DomainDataSource.  We also want to have an extra column which computes a value based on other data that exists in each row.

My approach to this scenario is to utilize the code sharing feature of RIA Services to pass across a property which computes the value on client-side.  As you will see, the DataGrid and DomainDataSource accommodate this approach rather nicely.

We’re going to keep things simple on the server-side for this example and not associate our Domain Service to any entities in a database.  So add a new DomainService called “DemoService” but don’t associate it with any data.

Ok now that we have a Domain Service, lets create an entity object to work with in a class file called “Person.cs”:

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A common situation I run into is the need to access some element within a DataTemplate.  Silverlight isn't able to auto-generate strongly typed references to these elements in code behind.  In other words, adding the "x:Name=myElementName" property to the element doesn't matter from a code-behind standpoint.  However, we can use the x:Name in a different way to access our element at the right moment. Enter: Element-To-Element databinding.  I think many of us know how to bind to property of another element, but it is also possible to bind to the element itself.

The scenario:

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Someone on Silverlight.net was having trouble with this one so I worked up an example.  Here’s the Xaml:

Here’s the working version of it: