while (ex != null)
{
WriteExceptionLog(ex, fileName);
ex = ex.InnerException;
}

        /// <summary>
        /// 将异常处理成字符串的形式,然后写入文件
        /// </summary>
        /// <param name="ex"></param>
        /// <param name="fileName"></param>
        private void WriteExceptionLog(Exception ex, string fileName)
        {
            WriteLog(string.Format("错误信息:{0}{1}异常类型:{2}{1}程序集:{3}{1}方法:{4}{1}跟踪栈信息:{1}{5}{1}",
                  ex.Message,
                  Environment.NewLine,
                  ex.GetType(),
                  ex.Source,
                  ex.TargetSite,
                  ex.StackTrace),
                  fileName);//写入文件
        }