Figuring out Silverlight namespaces and assemblies

Question

Often when you find examples of Silverlight code on the web it may only contain a snippet of code rather than the full set needed to make it work. This causes me immense frustration when I am trying to work out what namespace and/or assembly declaration to use at the top of the xaml file.

For example, take the following snippet (which shows how to add a list of items as a static resource)

<UserControl.Resources>   
   <controls:ObjectCollection x:Key="SampleData">  
      <sys:String>User 1</sys:String>  
      <sys:String>User 2</sys:String>  
      <sys:String>User 3</sys:String>  
   </controls:ObjectCollection>  
</UserControl.Resources> 

How is it possible for me to determine what namespace and assembly this guy used as the "controls" alias???