(dir -include *.cs,*.xaml -recurse | select-string .).Count

Add extension types as necessary. Note that it DOES include comments in the line count.

Here’s the stackoverflow article where this originated from, I needed something that would run outside of the main solution to take into account all the additional projects and files, so a plugin was not going to work.

http://stackoverflow.com/questions/1244729/how-do-you-count-the-lines-of-code-in-a-visual-studio-solution