By default in VS2011, you won’t be able to debug WinRT Components that you consume from C#/JS projects. This is because unmanaged code debugging is disable by default.
To workaround this, you need to go to Solution Explorer, right-click your Startup project (C# or JS), and select Properties menu. Under the Debug tab, check the last checkbox named: Enabled unmanaged code debugging.
After you do this little change, you will be able to step into your WinRT components when you’re debugging your Metro app.