/// <summary>
/// 频率恒定计时器
/// </summary>
    public class FixedRateTimer
    {
/// <summary>
/// 构造方法
/// </summary>
/// <param name="start">启动后延迟多久开始执行</param>
/// <param name="interval">下次执行距离这次执行开始的时间</param>
/// <param name="action">任务委托</param>
/// <param name="state">任务状态参数</param>
/// <param name="concurrent">是否允许并行
/// <remarks>如果允许并行，同一时间可能有几个任务同时执行;
/// 如果不允许,当新任务发现上次任务正在运行时，将忽略此次任务</remarks>
/// </param>
        public FixedRateTimer(TimeSpan start, TimeSpan interval, TimerCallback action,
object state = null, bool concurrent = false)
        {
            _action = action;
            _isConcurrent = concurrent;

            _start = start;
            _interval = interval;
            _state = state;
        }

private void TimerAction(object s)
        {
//增加正在执行任务个数
            Interlocked.Increment(ref _jobCount);
if (!_isConcurrent)
            {
//:任务无法并行执行，所以必须串行化

//当无任务执行(_isRunning==0)时更改状态为运行(_isRunning=0),
//然后开始执行新任务,因为代码可能多线程执行，所以用原子操作
                if (Interlocked.CompareExchange(ref _isRunning,1,0) == 0)
                {
                    _action(s);
//更改状态为无任务运行
                    Interlocked.Exchange(ref _isRunning, 0);
                }
            }
else
            {
//无串行约束，直接执行
                _action(s);
            }
//减少正在执行任务个数
            Interlocked.Decrement(ref _jobCount);
        }

/// <summary>
/// 开始计时
/// </summary>
        public void Start()
        {
            _isRunning = 0;
            _timer = new Timer(TimerAction, _state, _start, _interval);
        }

/// <summary>
/// 结束计时
/// </summary>
        public void Stop()
        {
            _timer.Dispose();
            WaitUtilFinish();
            _timer = null;
            _isRunning = 0;
        }

/// <summary>
/// 等待已经开始执行的任务执行完
/// </summary>
        private void WaitUtilFinish()
        {
while (_jobCount != 0)
            {
                Thread.Sleep(_interval);
            }
        }

//用来在不允许并发时保持任务串行
        private int _isRunning = 0;
private int _jobCount = 0;
private bool _isConcurrent = false;

private TimerCallback _action = null;
private Timer _timer = null;

private TimeSpan _start;
private TimeSpan _interval;
private Object _state;
    }

 1            FixedRateTimer timer = new FixedRateTimer(TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(2),
 2                 s =>
 3                 {
 4                     Console.WriteLine("开始运行：" + DateTime.Now);
 5                     Thread.Sleep(5000);
 6                     Console.WriteLine("结束运行：" + DateTime.Now);
 7                 }, null);
 8             timer.Start();
 9             Thread.Sleep(TimeSpan.FromSeconds(20));
10             timer.Stop();
11             Console.WriteLine("再试一次");
12             timer.Start();
13             Thread.Sleep(TimeSpan.FromSeconds(20));
14             timer.Stop();

    public class FixedDelayTimer
    {        
/// <summary>
/// 构造方法
/// </summary>
/// <param name="start">启动后延迟多久开始执行</param>
/// <param name="interval">下次执行开始距离这次执行结束的时间</param>
/// <param name="action">任务委托</param>
/// <param name="state">任务状态参数</param>
        public FixedDelayTimer(TimeSpan start, TimeSpan interval, TimerCallback action, object state = null)
        {
            _action = action;

            _start = start;
            _interval = interval;
            _state = state;
        }

private void TimerAction(object s)
        {
            Thread.Sleep(_start);
while (_isExit == 0)
            {
                _action(s);
                Thread.Sleep(_interval);
            }
        }

/// <summary>
/// 开始计时
/// </summary>
        public void Start()
        {
            _isExit = 0;
            _thread = new Thread(new ParameterizedThreadStart(TimerAction));
            _thread.Start();
        }

/// <summary>
/// 结束计时
/// </summary>
        public void Stop()
        {
//通知线程退出
            Interlocked.Exchange(ref _isExit, 1);
//等待线程执行完毕
            _thread.Join();
            _thread = null;
        }

private int _isExit = 0;//是否退出计时器循环

private TimerCallback _action = null;
private Thread _thread = null;

private TimeSpan _start;
private TimeSpan _interval;
private Object _state;
    }

 1             FixedDelayTimer timer = new FixedDelayTimer(TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(2),
 2                 s =>
 3                 {
 4                     Console.WriteLine("开始运行：" + DateTime.Now);
 5                     Thread.Sleep(5000);
 6                     Console.WriteLine("结束运行：" + DateTime.Now);
 7                 }, null);
 8             timer.Start();
 9             Thread.Sleep(TimeSpan.FromSeconds(20));
10             timer.Stop();
11             Console.WriteLine("再试一次");
12             timer.Start();
13             Thread.Sleep(TimeSpan.FromSeconds(20));
14             timer.Stop();