public double CalculatePercentChanged() { string page1 = _cache; string page2 = Helpers.WebHelper.DownloadWebPage(_url); if (page2 == "") { Error(); return -1.0; } diff_match_patch difflib = new diff_match_patch(); List<Diff> list = difflib.diff_main(page1, page2); double levenshtein = difflib.diff_levenshtein(list); double length = (page1.Length > page2.Length) ? page1.Length : page2.Length; double percentDifferent = levenshtein / length * 100; return percentDifferent; }