When to Write Custom Controls in Font

Creator Code 128 Code Set A in Font When to Write Custom Controls

When you find that none of the existing Silverlight controls do exactly what you want, creating a custom control is not always the solution. In fact, in most cases, you should be able to get by without writing custom controls. Due to the flexibility built into the Silverlight 2 controls, you can usually modify an existing one to suit your needs. As a general rule, if your goal is to modify the appearance of a control, there is no need to write a custom control. Silverlight controls that are built properly, following Microsoft s best practices, will adopt the Parts and States model, which calls for complete separation of the logical and visual aspects of your control. Due to this separation, developers can change the appearance of controls, and even change transitions of the controls between different states, without needing to write custom controls.

So, just when is creating a custom control the right way to go Here are the primary reasons for writing custom controls: Abstraction of functionality: When developing your applications, you may need to implement some functionality that can be achieved using Silverlight 2 s out-of-thebox support. However, if this functionality needs to be reused often in your application, you may choose to create a custom control that abstracts the functionality, in order to simplify the application. An example of this would be if you wanted to have two text boxes next to each other for first and last names. Instead of always including two TextBox controls in your XAML, you could write a custom control that would automatically include both text boxes and would abstract the behavior surrounding the text boxes. Modification of functionality: If you would like to change the way a Silverlight 2 control behaves, you can write a custom control that implements that behavior, perhaps inheriting from an existing control. An example of this would be if you wanted to create a button that pops up a menu instead of simply triggering a click method. Creation of new functionality: The most obvious reason for writing a custom control in Silverlight 2 is to add functionality that does not currently exist in Silverlight. As an example, you could write a control that acts as a floating window that can be dragged and resized. Although these are valid reasons for creating custom controls, there is one more resource you should check before you do so: the Silverlight Control Toolkit.

Upon the release of Silverlight 2, Microsoft announced the Silverlight Control Toolkit, an open source project located on CodePlex at http://www.codeplex.com/SilverlightToolkit. This toolkit provides additional components and controls that you can download for use in your Silverlight applications. For example, it includes the fully functional charting controls shown in Figure 11-1. Microsoft s target is to eventually have more than 100 controls available through this open source toolkit. For developers, this means that as Silverlight 2 matures, more and more controls will be available for use in your applications.

The Silverlight Control Toolkit contains four quality bands that describe the specific control s maturity level: experimental, preview, stable, and mature. With the initial announcement of the Silverlight Control Toolkit, the following twelve controls (six within the preview band and six in the stable band) are available for download (including the full source code): AutoCompleteBox NumericUpDown Viewbox Expander ImplicitStyleManager Charting TreeView DockPanel WrapPanel

Label HeaderedContentControl HeaderedItemsControl This toolkit is an excellent resource for Silverlight 2 developers. You can use these controls as is in your applications, or you can use the source code to modify your own controls. They are also a great way to learn how to build custom controls, because you can examine their source code. In order to understand that source code, you will need to know about the Silverlight control model.