A Markup Extension is a class that decides at runtime how to set a property’s value. Markup extensions allow code to be run at XAML parse time for both properties and event handlers.
In Silverlight 4 we got some different Markup Extensions:
- Binding
Text=”{Binding Path=FirstName, Mode=TwoWay}” - StaticResource
Foreground=”{StaticResource BlueSolidColor}” - TemplateBinding
VerticalAlignment=”{TemplateBinding VerticalContentAlignment}” - NullExtension
Background={x:Null} - RelativeSource
DataContext="{Binding RelativeSource={RelativeSource TemplatedParent}}"
With Silverlight 5 we get Custom Markup Extensions allowing us to write more specific and complex Markup Extensions.
Jeff Prosise’s have written a good sample here and Jeremy Likness have written about getting creating a custom markup extension that uses MEF to satisfy imports on object instances declared in XAML here.
