廢話不說，直接上代碼

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Utilities
{
    public class TXTLogHelper
    {
        /// <summary>
        /// 對某些操作進行TXT日誌記錄
        /// </summary>
        public static void
 
 LogBackup(string LogString)
        {
            string logFolder = GetOrCreateLogFilePath();
            string logFile = GetBackupLogFileName();
            
            FileInfo file = new FileInfo(logFile);
            FileStream fs = file.Open(FileMode.Append, FileAccess.Write);
            byte
 
[] bytes = Encoding.UTF8.GetBytes(LogString);
            fs.Write(bytes, 0, bytes.Length);
            fs.Flush();
            fs.Close();
            fs.Dispose();
        }

        //獲取備份目錄路徑，如果不存在則創建
        private static string GetOrCreateLogFilePath()
        {
            string backupFolder = System.Environment.CurrentDirectory + "
 
\\log";
            if (!Directory.Exists(backupFolder))
                Directory.CreateDirectory(backupFolder);
            return backupFolder;
        }

        private static string GetBackupLogFileName()
        {
            //為了防止數據量過大，按照日期每天生成一個日誌文件
            string logFileId = DateTime.Now.ToString("yyyy-MM-dd");
            return GetOrCreateLogFilePath() + "\\" + logFileId + ".txt";
        }
    }
}

20181015記錄一個簡單的TXT日誌類