Or, you could use an editor more advanced than notepad.exe and use a "toggle comment" command which which allows you to switch between //line 1 //line 2

Or, you could use an editor more advanced than notepad.exe and use a "toggle comment" command which which allows you to switch between //line 1 //line 2 //... //line N ...and... line 1 line 2 ... line N ...with more flexibility than using a syntax trick.