As you know with Resharper when you press “Ctrl+B” you navigate to the declaration of thing you are currently located on. But when you press that on double for example? In Visual Studio you are able to navigate to the metadata view, but Resharper provides 3 options: Object Browser, MetadataView and actual .Net Framework code. If you have no appropriate mscorlib.pdb Resharper will download it like on the picture below:

So finally you are able to see this code:

This is one of things why I love Resharper, no need to go for another tool like Reflector.