Using Resource Dictionarys to clean up Generic.xaml

If you're ever done any sizable amount of control development in Silverlight 2 then you'll know that managing Generic.xaml can be a real pain. A couple of complicated controls including things like the Visual State Manager means it won't be long before you're looking at hundreds of lines of xaml that's not easily managed from Blend.

Thankfully in Silverlight 3 we have Merged Resource Dictionaries, they can certainly help organise the styles, templates and other resources in your application, but they can also help break up Generic.xaml into more management chunks. In this example we'll be break up the FocusPanel we created some months ago.

In Visual Studio you can add a new Resource Dictionary from the "Add New Item" under the Silverlight category. Now you can copy the styles out of Generic.xaml into the new Resource Dictionary, create as many as you want, I tend to organise as it as a Resource Dictionary per control (which may have a few styles for sub controls). Important: Make sure your new Resource Dictionary has a Build Action of "Resource", you can also clear the Custom Tool property if you want.

Now that we have our new Resource Dictionary we need to merge it into Generic.xaml. The syntax is exactly the same as using ResourceDictionary.MergedDictionaries in your normal Silverlight application, the only gotcha is the Uri format, make sure to include the assembly name in the Uri as follows.

        <ResourceDictionary Source="/CompiledExperience.Core.Controls;component/Themes/FocusPanel.xaml" />
        <ResourceDictionary Source="/CompiledExperience.Core.Controls;component/Themes/ContentPanel.xaml" />
        <ResourceDictionary Source="/CompiledExperience.Core.Controls;component/Themes/Upload.xaml" />
        <ResourceDictionary Source="/CompiledExperience.Core.Controls;component/Themes/ServiceActivity.xaml" />

Hope this helps someone.