public class Logger
    {
        public static void WriteLog(string rootFolder, string message)
        {
            message = DateTime.Now.ToString("yyyy/MM/dd hh:mm") + " - " + message;
            string[] lines = { message };

            var filePath = rootFolder + @"\" + DateTime.Now.ToString("yyyy-MM-dd") + @"_Site.log";

            // This text is added only once to the file.
            if (!File.Exists(filePath))
            {
                // Create a file to write to.
                System.IO.File.WriteAllLines(filePath, lines);
            }
            else
            {
                File.AppendAllText(filePath, message + Environment.NewLine);
            }

        }
    }