Debugging Silverlight in Firefox, Safari
If you’re already familiar with attaching to processes in Visual Studio (or WinDbg), this is nothing new. However, I’ve seen this question come up a few times—particularly with people coming over from competing technologies.
In Visual Studio, just select the “Attach to process” option (available in the Debug or Tools menu, depending on your workspace view) and select the type of code you want to debug, Silverlight in this case, and the process you want to debug. This applies to any process that is hosting a Silverlight instance.
You should be aware that this general advice applies to all sorts of applications. For example, if you want to debug the behavior of your Silverlight control library during design-time operations, you could use one instance of the debugger to attach to the application that is rendering the design surface. (E.g., attach to Blend or event to another instance of Visual Studio.)