C#-----定时器的几种实现

   1. System.Windows.Forms.Timer

     计时器最宜用于 Windows 窗体应用程序中，并且必须在窗口中使用，适用于单线程环境,

在此环境中, UI 线程用于执行处理。 它要求用户代码提供 UI 消息泵, 并且始终从同一线程操作, 或将调用封送到

其他线程。Windows 窗体计时器组件是单线程的, 且限制为55毫秒的准确度，准确性不高

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace TestTimer
{
    public partial class frmTimerDemo : Form
    {
        private System.Windows.Forms.Timer timerGetTime;
        public frmTimerDemo()
        {
            InitializeComponent();
        }

        private void frmTimerDemo_Load(object sender, EventArgs e)
        {
            //创建定时器
            timerGetTime = new System.Windows.Forms.Timer();
            //设置定时器属性
            timerGetTime.Tick+=new EventHandler(HandleTime);
            timerGetTime.Interval = 1000;
            timerGetTime.Enabled = true;
            //开启定时器
            timerGetTime.Start();
        }

        public void HandleTime(Object myObject, EventArgs myEventArgs)
        {
            labelTime.Text = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");
        }

        private void frmTimerDemo_FormClosed(object sender, FormClosedEventArgs e)
        {
            //停止定时器
            timerGetTime.Stop();
        }
    }
}

   2. System.Timers.Timer

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Timers;
using System.Windows.Forms;

namespace TimerDemo
{
    public partial class frmTimerDemo : Form
    {
        private static System.Timers.Timer aTimer;
        public frmTimerDemo()
        {
            InitializeComponent();
        }

        private void frmTimerDemo_Load(object sender, EventArgs e)
        {
            aTimer = new System.Timers.Timer();
            aTimer.Elapsed += new System.Timers.ElapsedEventHandler(OnTimedEvent);
            aTimer.Interval = 1000;
            aTimer.Enabled = true;
            aTimer.Start();
        }

        public void OnTimedEvent(Object source, ElapsedEventArgs e)
        {
            this.labelTime.Text = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");
        }

        private void frmTimerDemo_FormClosed(object sender, FormClosedEventArgs e)
        {
            aTimer.Stop();
        }
    }
}

   3. System.Threading.Timer

     线程计时器也不依赖窗体，是一种简单的、轻量级计时器，它使用回调方法而不是使用事件，并由线程池线程提供支持

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

namespace TimerDemo
{
    class Program
    {
        int TimesCalled = 0;

        void Display(object state)
        {
            Console.WriteLine("{0} {1} keep running.", (string)state, ++TimesCalled);
        }

        static void Main(string[] args)
        {
            Program p = new Program();
            //2秒后第一次调用，每1秒调用一次
            System.Threading.Timer myTimer = new System.Threading.Timer(p.Display, "Processing timer event", 2000, 1000);
            Console.WriteLine("Timer started.");
            Console.ReadLine();
        }
    }
}