我們在寫winfrom時經常會用到定時器，比如客戶端通過socket定時向伺服器傳送檢測包等。.netframework提供了一個定時器控制元件System.Windows.Forms.Timer，使用很方便。
 
其實通過C#多執行緒也可以實現定時器功能。我的做法大致為：新開一個執行緒用於計時，當時間間隔過後用事件timerover實現主窗體中的定時函式，再通過呼叫contro.invoke方法返回主窗體執行緒執行定時後的操作。
 
 
先定義兩個類，timer類用於管理和配置定時器，interval_date用於計算兩個時刻的間隔（例如2010年1月1日和2012年12月26日之間的毫秒），單位是毫秒，因此定時器的設定範圍理論上可以無限大。原理不多說，下面放程式碼：

timer類程式碼：

public class timer 
   { 
       int count = 0; 
       public delegate void Deletimerover(int count); 
       public event Deletimerover timerover; 
       private int time; 
       public int Time 
       { 
           set { time = value; } 
           get { return time; } 
       } 
       private bool enable; 
       public bool Enable 
       { 
           set { enable = value; } 
       } 
       public timer() 
       { 
       } 
       public timer(int t) 
       { 
           time = t; 
       } 
       public void start_time() 
       { 
           Thread rd = new Thread(new ThreadStart(start)); 
           rd.IsBackground = true; 
           count = 0; 
           rd.Start(); 
       } 
       private void start() 
       { 
           DateTime dt_tem = DateTime.Now; 
           interval_date interval = new interval_date(); 
           while (interval.interval_millisec(dt_tem,DateTime.Now) < time) ; 
           if (!enable) 
           { 
               return; 
           } 
           else 
           { 
               timerover(++count); 
               start(); 
           } 
       } 
   }   
 

interval_date類程式碼：

public class interval_date 
   { 
       public long interval_millisec(DateTime dt1,DateTime dt2) 
       { 
           long interval = 0; 
           interval += com_year(dt1,dt2); 
           interval += com_month(dt1,dt2); 
           interval += com_day(dt1,dt2); 
           interval += com_hour(dt1, dt2); 
           interval += com_minute(dt1, dt2); 
           interval += com_second(dt1, dt2); 
           interval += com_millisecond(dt1, dt2); 
           return interval; 
       } 
       private long com_year(DateTime dt1, DateTime dt2) 
       { 
           int year1 = dt1.Year; 
           int year2 = dt2.Year; 
           long interval = 0; 
           if (year1 != year2) 
           { 
               for (int i = year1 + 1; i < year2; i++) 
               { 
                   for(int j = 1; j <= 12; j++) 
                   { 
                       interval += DateTime.DaysInMonth(i, j); 
                   } 
               } 
           } 
           interval = interval * 24 * 3600 * 1000; 
           return interval; 
       } 
       private long com_month(DateTime dt1, DateTime dt2) 
       { 
           int year1 = dt1.Year; 
           int year2 = dt2.Year; 
           int month1 = dt1.Month; 
           int month2 = dt2.Month; 
           long interval = 0; 
           if (year1 != year2) 
           { 
               for (int i = month1 + 1; i <= 12; i++) 
               { 
                   interval += DateTime.DaysInMonth(year1, i); 
               } 
               for (int i = 1; i < month2; i++) 
               { 
                   interval += DateTime.DaysInMonth(year2, i); 
               } 
           } 
           else 
           { 
               for (int i = month1+1; i < month2; i++) 
               { 
                   interval += DateTime.DaysInMonth(year1, i); 
               } 
           } 
           interval = interval * 24 * 3600 * 1000; 
           return interval; 
       } 
       private long com_day(DateTime dt1,DateTime dt2) 
       { 
           int year1 = dt1.Year; 
           int year2 = dt2.Year; 
           int month1 = dt1.Month; 
           int month2 = dt2.Month; 
           int day1 = dt1.Day; 
           int day2 = dt2.Day; 
           long interval = 0; 
           if (year1 == year2 && month1 == month2) 
           { 
               if(day2 == day1) 
               { 
                   return 0; 
               } 
               interval = day2-day1-1; 
           } 
           else 
           { 
               interval += DateTime.DaysInMonth(year1, month1) - day1; 
               interval += day2-1; 
           } 
           interval = interval * 24 * 3600 * 1000; 
           return interval; 
       } 
       private long com_hour(DateTime dt1, DateTime dt2) 
       { 
           long interval = 0; 
           if (dt1.Year == dt2.Year && dt1.Month == dt2.Month && dt1.Day == dt2.Day) 
           { 
               if (dt1.Hour == dt2.Hour) 
               { 
                   return 0; 
               } 
               interval += dt2.Hour - dt1.Hour - 1; 
           } 
           else 
           { 
               interval += 24 - dt1.Hour - 1; 
               interval += dt2.Hour; 
           } 
           interval = interval * 3600 * 1000; 
           return interval; 
       } 
       private long com_minute(DateTime dt1, DateTime dt2) 
       { 
           long interval = 0; 
           if (dt1.Year == dt2.Year && dt1.Month == dt2.Month && dt1.Day == dt2.Day && dt1.Hour == dt2.Hour) 
           { 
               if (dt1.Minute == dt2.Minute) 
               { 
                   return 0; 
               } 
               interval += dt2.Minute - dt1.Minute - 1; 
           } 
           else 
           { 
               interval += 60 - dt1.Minute - 1; 
               interval += dt2.Minute; 
           } 
           return interval * 60 * 1000; 
       } 
       private long com_second(DateTime dt1, DateTime dt2) 
       { 
           long interval = 0; 
           if (dt1.Year == dt2.Year && dt1.Month == dt2.Month && dt1.Day == dt2.Day && dt1.Hour == dt2.Hour && dt1.Minute == dt2.Minute) 
           { 
               if (dt1.Second == dt2.Second) 
               { 
                   return 0; 
               } 
               interval += dt2.Second - dt1.Second - 1; 
           } 
           else 
           { 
               interval += 60 - dt1.Second - 1; 
               interval += dt2.Second; 
           } 
           return interval * 1000; 
       } 
       private long com_millisecond(DateTime dt1, DateTime dt2) 
       { 
           long interval = 0; 
           if (dt1.Year == dt2.Year && dt1.Month == dt2.Month && dt1.Day == dt2.Day && dt1.Hour == dt2.Hour && dt1.Minute == dt2.Minute && dt1.Second == dt2.Second) 
           { 
               interval += dt2.Millisecond - dt1.Millisecond; 
           } 
           else 
           { 
               interval += 1000 - dt1.Millisecond; 
               interval += dt2.Millisecond; 
           } 
           return interval; 
       } 
   }  
 

最後就是使用方式了

public partial class Form1 : Form 
   { 
       public timer newtimer = new timer(); 
       delegate void Time(int count); 
       public void TimeOver(int count) 
       { 
           labelX1.Text = count.ToString(); 
       } 
       public Form1() 
       { 
           InitializeComponent(); 
           newtimer.Time = 1000; 
           newtimer.timerover +=new timer.Deletimerover(newtimer_timerover); 
       } 
       void newtimer_timerover(int count) 
       { 
           Time dd = new Time(TimeOver); 
           this.Invoke(dd, new object[] { count}); 
       } 
       private void buttonX1_Click(object sender, EventArgs e) 
       { 
           buttonX1.Enabled = false; 
           newtimer.Enable = true; 
           newtimer.Time = int.Parse(textBoxX1.Text); 
           newtimer.start_time(); 
       } 
       private void buttonX2_Click(object sender, EventArgs e) 
       { 
           newtimer.Enable = false; 
           buttonX1.Enabled = true; 
           labelX1.Text = "0"; 
           textBoxX1.Text = "1000"; 
       } 
   } 

一個文字框兩個按鈕，按鈕一用來開啟定時器，按鈕二用來複位。
通過簡單的驗證，這種方法和.netframework提供的timer控制元件實現的定時誤差在個位數（毫秒），也可以嘗試用更精確的方法來測試一下。