C#中一个异步日志系统的实现

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

namespace XXX
{
	public class AsyncLogFile
	{
		private Queue<string> Q;
		private AutoResetEvent EV;
		private Thread TH;
		private string PID;
		private bool Exit = false;
		private string mFilename;

		public AsyncLogFile(string filename, uint maxline = uint.MaxValue)
		{
			mFilename = filename;
			Start(maxline);
		}

		private void Start(uint maxline)
		{
			try
			{
				RotateLog(maxline);
				Q = new Queue<string>();
				EV = new AutoResetEvent(false);
				TH = new Thread(DoTheWork);
				PID = System.Diagnostics.Process.GetCurrentProcess().Id.ToString("00000");
				TH.Name = $"AsyncLog {mFilename}";
				TH.Start();
			}
			catch { }
		}

		private void RotateLog(uint maxline)
		{
			try
			{
				if (System.IO.File.Exists(mFilename))
				{
					if (maxline <= 0) //dobbiamo azzerare il file
					{
						System.IO.File.Delete(mFilename);
					}
					else if (maxline != uint.MaxValue) 
					{
						String tmp = System.IO.Path.GetTempFileName();
						bool written = false;

						using (System.IO.StreamReader reader = new System.IO.StreamReader(new System.IO.FileStream(mFilename, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.None)))
						{
							ulong linecount = 0;
							while (reader.ReadLine() != null)
								linecount++;

							reader.BaseStream.Seek(0, System.IO.SeekOrigin.Begin);

							if (linecount > maxline)
							{
								ulong lines_to_delete = linecount - maxline;
								using (System.IO.StreamWriter writer = new System.IO.StreamWriter(tmp))
								{
									string line;
									while (lines_to_delete-- > 0)
										reader.ReadLine();
									while ((line = reader.ReadLine()) != null)
										writer.WriteLine(line);
								}
								written = true;
							}

							reader.Close();
						}

						if (written)
						{
							System.IO.File.Delete(mFilename);
							System.IO.File.Move(tmp, mFilename);
						}
						else
						{
							if (System.IO.File.Exists(tmp))
								System.IO.File.Delete(tmp);
						}
					}
				}
			}
			catch { }
		}

		internal void Stop()
		{
			Exit = true;
			EV.Set();
		}

		public void Log(string text)
		{
			try { Enqueue(text); }
			catch { }
		}

		private void Enqueue(string s)
		{
			lock (Q)
			{
				if (Q.Count < 10000)
					Q.Enqueue(s);   
			}

			EV.Set();
		}

		private void DoTheWork()
		{
			while (!Exit)
			{
				EV.WaitOne();

				if (Q.Count > 0)	//ho roba da scrivere
				{
					try
					{
						using (System.IO.StreamWriter writer = new System.IO.StreamWriter(mFilename, true))
						{
							while (Q.Count > 0) 
							{
								string s;

								lock (Q) { s = Q.Peek(); }

								writer.Write(s);
								System.Diagnostics.Debug.Write(s);

								lock (Q) { Q.Dequeue(); }

							}

							writer.Close();
						}
					}
					catch { Thread.Sleep(1); }
				}
			}
		}

		public bool ExistLog
		{ get { return System.IO.File.Exists(mFilename); } }

		public void ShowLog()
		{ System.Diagnostics.Process.Start(mFilename); }

	}
}