C# 记事本保存log

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Web;


public static class setLog
{
    /// <summary>
    /// 創建txt,并寫入
    /// </summary>
    /// <param name="logmsg">要寫入的信息</param>
    public static void SetLogTx(string logmsg)
    {
        //文件名
        DateTime dt = DateTime.Now;
        string path = System.AppDomain.CurrentDomain.BaseDirectory;
        string filename = dt.ToString("yyyy-MM-dd") + "_log.txt";

        //沒有則創建,同一天不創建多個
        FileStream fs;
        if (!File.Exists(path + filename))
        {
            fs = new FileStream(path + filename, FileMode.Create, FileAccess.Write);
        }
        else
        {
            fs = new FileStream(path + filename, FileMode.Open, FileAccess.Write);
        }

        //追加寫入
        StreamWriter sw = new StreamWriter(fs);
        long fl = fs.Length;
        fs.Seek(fl, SeekOrigin.Begin);
        sw.WriteLine(DateTime.Now.ToString() + " _S:_____" + logmsg + "_____End.\n");//開始寫入值
        //結束
        sw.Close();
        fs.Close();
    }


    /// <summary>
    /// 刪除大於7天的log文檔
    /// </summary>
    public static void deleteLogTxt()
    {
        string filePath = System.AppDomain.CurrentDomain.BaseDirectory;

        string[] files = Directory.GetFiles(filePath, "*_log.txt");
        foreach (var file in files)
        {
            FileInfo fi = new FileInfo(file);
            if ((DateTime.Now - fi.LastWriteTime).TotalDays > 7) //fi.CreationTime
            {
                fi.Delete();
            }
            else break;
        }

    }
}