2022 :
shift + up/down key : multi-line code editing
shift + option + up/down key : copy the single line
Multi-Line Code Editing in Visual Studio 2017
Here’s a quick tip if you’ve ever wanted to edit multiple lines of code at once in Visual Studio. Simply position your cursor at a point in your code, then press and hold SHIFT and ALT. Next, press the up or down arrow to select the lines you want to edit. When you begin typing you will behold a gift from the gods – editing multiple lines at once!
http://patrickgoode.com/multi-line-code-editing-in-visual-studio-2017/
--------------------------
on a Mac
opt + shift