为什么定时器没有工作

[huerreson]

using System;
using System.Data;
using System.Data.SqlClient;
using System.Collections;
using System.ComponentModel;
using System.Web;
using System.Web.SessionState;
using System.Timers;
using System.Threading;
using System.Diagnostics;

namespace gift 
{
	/// <summary>
	/// Global 的摘要说明。
	/// </summary>
	public class Global : System.Web.HttpApplication
	{
		/// <summary>
		/// 必需的设计器变量。
		/// </summary>
		private System.ComponentModel.IContainer components = null;

		public Global()
		{
			InitializeComponent();
		}	
		
		protected void Application_Start(Object sender, EventArgs e)
		{
			Pub.UpFileClass.WriteContentToFile(Pub.GetSet.SitePath+"log/"+ DateTime.Now.ToShortDateString() +".txt" ,"["+DateTime.Now+"] 系统开始运行.",true,"utf-8");
			System.Timers.Timer myTimer = new System.Timers.Timer();
			myTimer.Elapsed += new ElapsedEventHandler(myTimer_Elapsed);
			myTimer.Interval = Pub.GetSet.AutoDelTimerInterval;
			myTimer.AutoReset = true;
			myTimer.Enabled = true;
			Pub.UpFileClass.WriteContentToFile(Pub.GetSet.SitePath+"log/"+ DateTime.Now.ToShortDateString() +".txt" ,"["+DateTime.Now+"]"+myTimer.Interval,true,"utf-8");
		}
 
		........（省略若干代码）
                private void myTimer_Elapsed(object source, ElapsedEventArgs e)
		{
			ThreadStart threadDelegat = new ThreadStart(DelExpiredBusiness);
			Thread myThread = new Thread(threadDelegat);
			if (Application["DelExpiredBusinessState"].ToString() != "Running")
			{
				myThread.Start();
			}
		}
		/// <summary>
		/// 删除过期信息
		/// </summary>
		/// <param name="sender"></param>
		/// <param name="e"></param>
		public void DelExpiredBusiness() 
		{
			Application.Lock();
			Application["DelExpiredBusinessState"] = "Running";
			Application.UnLock();

			SqlParameter[] param = new SqlParameter[]{new SqlParameter("@ExpiredDay",SqlDbType.Int),new SqlParameter("@RETURN_VALUE",SqlDbType.Int)};
			param[0].Value = 90;
			param[1].Direction  = ParameterDirection.ReturnValue;
			SqlDataReader rd = gift.Data.Provider.Global.getDataReader("sp_Business_expried_day",param);
			while(rd.Read())
			{
				try
				{
					Pub.UpFileClass.DeleteFile(rd["BPic"].ToString());
					Pub.UpFileClass.DeleteFile(rd["BHPic"].ToString());
				}
				catch
				{

				}
			}
			rd.Close();
			gift.Data.Provider.Global.NonQuery("delete from business where DATEDIFF(DAY,BValidate,GETDATE())>90");
			Application.Lock();
			Application["DelExpiredBusinessState"] = "End";
			Application.UnLock();
		}
		#region Web 窗体设计器生成的代码
		/// <summary>
		/// 设计器支持所需的方法 - 不要使用代码编辑器修改
		/// 此方法的内容。
		/// </summary>
		private void InitializeComponent()
		{    
			this.components = new System.ComponentModel.Container();
		}
		#endregion
	}
}

[johnwoo85]

    void Application_Start(object sender, EventArgs e) 
    {
        // 應用程式啟動時執行的程式碼
        System.Timers.Timer timer = new System.Timers.Timer(1000 *60);
        //AutoReset 属性为 true 时，每隔指定时间循环一次；
        //如果为 false，则只执行一次。
        timer.AutoReset = true;
        timer.Enabled = true;    
        timer.Elapsed += new System.Timers.ElapsedEventHandler(timer_Elapsed);
        
    }
System.Timers.Timer timer = new System.Timers.Timer(1000 *60);

[ljm66]

System.Timers.Timer timer 定义为全局变量就好了