How do I duplicate a whole line in Emacs?

Question

I saw this same question for VIM and it has been something that I myself wanted to know how to do for Emacs. In ReSharper I use CTRL-D for this action. What is the least num

Answer 1

As mentioned in other answers, binding key strokes to lisp code is a better idea than binding them to another key strokes. With @mw's answer, code duplicates the line and moves the mark to end of new line. This modification keeps the mark position at same column on the new line:

fun duplicate-line ()
  (interactive)
  (let ((col (current-column)))
    (move-beginning-of-line 1)
    (kill-line)
    (yank)
    (newline)
    (yank)
    (move-to-column col)))