In this post I want to explain why I don't like debugging, and prefer instead to use unit testing where I work in tiny sections.
To put this post in context, can first I encourage you to read:
I wait here in the meantime 
We just faced an interesting problem on one of our dev's computers.
He is not able to debug any VS2010 solution: Windows Forms, WPF, Web Forms… There is no chance to debug anything on his 64bit machine.
If you get this nice error message, you are probably lost, because there is no hints on WHY!!!???
Microsoft Visual Studio
---------------------------
Unable to start debugging. The Silverlight Developer Runtime is not installed. Please install a matching version.
When you create a Silverlight project, VS looks for the HKLM,SOFTWARE\Microsoft\Silverlight\Components\Debugging reg key to make sure you have the dev runtime.
And when you debug, Silverlight looks for the HKLM\Software\Microsoft\.NETFramework\DbgpackShimPath reg key.
Thanks Amy!! Check out her blog about Silverlight and web dev
So your registry should have those keys and pointing to
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Silverlight\Components\Debugging
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework
Both these keys should point to the same version (see my examples for Silverlight RTM)
If you encounter
"The symbol file pdb does not match the module"
Try to look in
Debug -> Windows -> Modules
Ctrl-D, M
there you can see where vs2008 tries to load the .pdb file.
SOLUTION
Rebuild your dll in DebugMode and deploy it there!
The symbol file im.pdb does not match the module - MSDN Forums
