"Can this be done with a single Regex?"
No.
To expand a little, in theory it could be done. But in practice the regex would be so complex that it would take more time to develop and debug than it is worth. Think about it:
Is that a comment? Or commented out code?
If we look at the following line
Then yes, it is commented out code.
If we look at a different following line:
Then it isn't.
Now, write a regex that works for those two. Now replace "Console" with "MyClass" and write one that handles that as well...