写入文件

public static string foldUrl = FM.Core.Utility.ConfigHelper.Instance.GetAppSetting("WriteLogFileUrl");
        public static string fileUrl = DateTime.Now.ToString("yyyy-MM-dd") + ".txt";
        /// <summary>
        /// 日志写入
        /// </summary>
        /// <param name="str"></param>
        public static void WriteLog(string str)
        {
            //文件夹地址
            if (!Directory.Exists(foldUrl))
                Directory.CreateDirectory(foldUrl);
            //文件地址
            string strFileUrl = foldUrl + fileUrl;
            System.IO.StreamWriter sw = null;
            if (!System.IO.File.Exists(strFileUrl))
                sw = System.IO.File.CreateText(strFileUrl);
            else
                sw = new System.IO.StreamWriter(strFileUrl, true);
            sw.BaseStream.Seek(0, System.IO.SeekOrigin.End);
            sw.WriteLine(str);
            sw.Flush();
            sw.Close();
        }