I used Ctrl+Shift+F. Next, put a \n in the search box and enable regular expressions box. Then in the find results, in the end of the screen are the number of files searched and lines of code found.
You can use [^\n\s]\r\n to skip blank and space-only lines (credits to Zach in the comments).
cloc is an excellent commandline, Perl-based, Windows-executable which will break down the blank lines, commented lines, and source lines of code, grouped by file-formats.
Now it won't specifically run on a VS solution file, but it can recurse through directories, and you can set up filename filters as you see fit.
Here's the sample output from their web page:
prompt> cloc perl-5.10.0.tar.gz
4076 text files.
3883 unique files.
1521 files ignored.
http://cloc.sourceforge.net v 1.07 T=10.0 s (251.0 files/s, 84566.5 lines/s)
-------------------------------------------------------------------------------
Language files blank comment code scale 3rd gen. equiv
-------------------------------------------------------------------------------
Perl 2052 110356 112521 309778 x 4.00 = 1239112.00
C 135 18718 22862 140483 x 0.77 = 108171.91
C/C++ Header 147 7650 12093 44042 x 1.00 = 44042.00
Bourne Shell 116 3402 5789 36882 x 3.81 = 140520.42
Lisp 1 684 2242 7515 x 1.25 = 9393.75
make 7 498 473 2044 x 2.50 = 5110.00
C++ 10 312 277 2000 x 1.51 = 3020.00
XML 26 231 0 1972 x 1.90 = 3746.80
yacc 2 128 97 1549 x 1.51 = 2338.99
YAML 2 2 0 489 x 0.90 = 440.10
DOS Batch 11 85 50 322 x 0.63 = 202.86
HTML 1 19 2 98 x 1.90 = 186.20
-------------------------------------------------------------------------------
SUM: 2510 142085 1564A simple solution is to search in all files. Type in "*" while using wildcards. Which would match all lines. At the end of the find results window you should see a line of the sort:
Matching lines: 563 Matching files: 17 Total files searched: 17
Of course this is not very good for large projects, since all lines are mached and loaded into memory to be dispayed at the find results window.
Reference: