With quick maturing of Silverlight, the application range of Silverlight has already gone beyond media player and mini games development. We have started building various applications with Silverlight, including enterprise-level projects. In order to make the applications extensible, robust, an outstanding framework is integrant. Here, let's compare several open source projects which adopts Silverlight frameworks.
Silverlight.FX
Silverlight.FX is a light-weight application framework, providing a service model, an IoC container, support for theming, view model (M-V-VM), navigation and MVC etc. Besides, SilverlightFX can be considered as Toolkit, because it provides a small set of enhanced controls, support for Forms and Windows, master page like containers, layout controls and data-bound controls. It also provides a procedural animation framework capable of implementing tweens and interpolations and easing behaviors.
In a word, Silverlight.FX is very powerful. But its assembly is far to 167K by providing too much functions. I think it means encumbrance to small Silverlight application. Dividing SilverLight.Fx into Framework, Toolkit and even more files will be better to meet user's specific requirement.
The author of Silverlight.FX is Nikhil Kothari, who is a senior and well-known software architect in Microsoft. So it is strongly recommended to learn this Framework even though you don't plan to use it.
PureMVC
PureMVC is a light-weight framework for creating applications based upon the classic Model, View and Controller concept. It supports multiple programming languages (ActionScript, C#, PHP, Java .etc) and platforms （Flex, Silverlight, PHP, Ruby etc）. Since PureMVC is all-purpose, the original specialty of silverlight has not been presented very well.
Composite Application Library (CAL) for WPF and Silverlight
The target of CAL is to use proved design patterns to help you create a complex application. Owing to CAL lays special emphasis on Enterprise application, the size of CAL will be too large to be suitable for small Silverlight application development. CAL supports Silverlight and WPF at the same time, which indicates a mutual conversion can be easily realized between WPF and Sliverlight.
Composite Application Library is developed by Microsoft, so there are plenty of QuickStarts, hands-on labs, and detailed documentations to help you learn.
CSLA .NET for Silverlight
CSLA.NET framework is a mature framework. But I am not familiar with it, just list it here for your reference.
We cannot affirm which Silverlight framework is the best in all conditions, however, you could choose the most suitable one tailored to your specific requirements. To me, Silverlight.FX can meet the need of most projects.
