在C#中，你可以使用System.IO.File和System.Diagnostics.EventLog類來記錄監控日志。以下是一個簡單的示例，展示了如何創建一個文件監視器來記錄日志：

using System;
using System.IO;
using System.Text;
using System.Threading.Tasks;
using System.Diagnostics;

namespace Watcher
{
    class Program
    {
        static void Main(string[] args)
        {
            string folderPath = @"C:\path\to\folder";
            string logFileName = "watcher.log";
            string logFilePath = Path.Combine(folderPath, logFileName);

            // 確保日志文件存在
            if (!File.Exists(logFilePath))
            {
                File.Create(logFilePath);
            }

            // 創建一個監視器來監視文件夾中的文件更改
            FileSystemWatcher watcher = new FileSystemWatcher(folderPath);

            // 定義要監視的事件類型
            watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite
                                  | NotifyFilters.FileName | NotifyFilters.DirectoryName;

            // 注冊事件處理程序
            watcher.Changed += Watcher_Changed;
            watcher.Created += Watcher_Created;
            watcher.Deleted += Watcher_Deleted;
            watcher.Renamed += Watcher_Renamed;

            // 開始監視
            watcher.EnableRaisingEvents = true;

            Console.WriteLine("開始監視文件夾: " + folderPath);
            Console.WriteLine("日志文件: " + logFilePath);

            // 等待用戶按下任意鍵退出
            Console.ReadKey();

            // 停止監視并注銷事件處理程序
            watcher.EnableRaisingEvents = false;
            watcher.Changed -= Watcher_Changed;
            watcher.Created -= Watcher_Created;
            watcher.Deleted -= Watcher_Deleted;
            watcher.Renamed -= Watcher_Renamed;

            Console.WriteLine("監視已停止");
        }

        private static void Watcher_Changed(object source, FileSystemEventArgs e)
        {
            LogEvent("文件已更改: " + e.FullPath);
        }

        private static void Watcher_Created(object source, FileSystemEventArgs e)
        {
            LogEvent("文件已創建: " + e.FullPath);
        }

        private static void Watcher_Deleted(object source, FileSystemEventArgs e)
        {
            LogEvent("文件已刪除: " + e.FullPath);
        }

        private static void Watcher_Renamed(object source, RenamedEventArgs e)
        {
            LogEvent("文件已重命名: " + e.OldFullPath + " -> " + e.FullPath);
        }

        private static void LogEvent(string message)
        {
            // 獲取當前時間
            DateTime now = DateTime.Now;

            // 創建日志條目
            StringBuilder logEntry = new StringBuilder();
            logEntry.AppendLine($"{now}: {message}");

            // 將日志條目追加到日志文件中
            File.AppendAllText(logFilePath, logEntry.ToString());

            // 可選: 將日志條目寫入事件日志
            // EventLog.WriteEntry(logFilePath, message, EventLogEntryType.Information);
        }
    }
}

這個示例將監視指定的文件夾，并在文件更改時記錄日志。你可以根據需要修改folderPath和logFileName變量來指定要監視的文件夾和日志文件的路徑。