asp.net如何定时执行任务-CUTEPIG BLOG-可爱猪博客

根据不同需求，在web开发中，有时候我们可能要定时的执行一下任务，比如定时发布网站中的文章，这时我们就需要做一个定时执行更新的操作，但由于web的http是无状态的连接，如何才能时时进行任务的更新呢?方法还是有的！

原理：Global.asax 可以是asp.net中应用程序或会话事件处理程序，我们用到了Application_Start(应用程序开始事件)和Application_End(应用程序结束事件)。当应用程序开始时，启动一个定时器，用来定时执行任务YourTask()方法，这个方法里面可以写上需要调用的逻辑代码，可以是单线程和多线程。当应用程序结束时，如IIS的应用程序池回收，让asp.net去访问当前的这个web地址。这里需要访问一个aspx页面，这样就可以重新激活应用程序。

局限性：可以解决应用程序池自动或者手动回收，但是无法解决IIS重启或者web服务器重启的问题，当然这种情况出现的时候不多，而且如果有人访问你的网站的时候，又会自动激活计划任务了。

C#代码：

using System;  
using System.Data;  
using System.Configuration;  
using System.Collections;  
using System.Web;  
using System.Web.Security;  
using System.Web.SessionState;  
using System.Timers;  
using System.Net;  
using System.IO;  
using System.Text;  
using System.Threading;  
namespace cutepig.net  
{  
    public class Global : System.Web.HttpApplication  
    {  
        protected void Application_Start(object sender, EventArgs e)  
        {  
            //定义定时器  
            System.Timers.Timer myTimer = new System.Timers.Timer(5000);  
            myTimer.Elapsed += new ElapsedEventHandler(myTimer_Elapsed);  
            myTimer.Enabled = true;  
            myTimer.AutoReset = true;  
        }  
        void myTimer_Elapsed(object source, ElapsedEventArgs e)  
        {  
              try 
              {  
                    Log.SaveNote(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":AutoTask is Working!");  
                    YourTask();  
              }  
              catch (Exception ee)  
              {  
                    Log.SaveException(ee);  
              }  
        }  
        void YourTask()  
        {  
       		//在这里写你需要执行的任务  

        }  
        protected void Application_End(object sender, EventArgs e)  
        {  
            Log.SaveNote(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":Application End!");  
            //下面的代码是关键，可解决IIS应用程序池自动回收的问题  
            Thread.Sleep(1000);  
            //这里设置你的web地址，可以随便指向你的任意一个aspx页面甚至不存在的页面，目的是要激发Application_Start  
            string url = "http://home.cutepig.net";
            HttpWebRequest myHttpWebRequest = (HttpWebRequest)WebRequest.Create(url);  
            HttpWebResponse myHttpWebResponse = (HttpWebResponse)myHttpWebRequest.GetResponse();  
            Stream receiveStream = myHttpWebResponse.GetResponseStream();//得到回写的字节流  
        }  
    }  
}

using System;

using System.Data;

using System.Configuration;

using System.Collections;

using System.Web;

using System.Web.Security;

using System.Web.SessionState;

using System.Timers;

using System.Net;

using System.IO;

using System.Text;

using System.Threading;

namespace cutepig.net

{

public class Global : System.Web.HttpApplication

{

protected void Application_Start(object sender, EventArgs e)

{

//定义定时器

System.Timers.Timer myTimer = new System.Timers.Timer(5000);

myTimer.Elapsed += new ElapsedEventHandler(myTimer_Elapsed);

myTimer.Enabled = true;

myTimer.AutoReset = true;

}

void myTimer_Elapsed(object source, ElapsedEventArgs e)

{

try

{

Log.SaveNote(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":AutoTask is Working!");

YourTask();

}

catch (Exception ee)

{

Log.SaveException(ee);

}

void YourTask()

{

//在这里写你需要执行的任务

}

protected void Application_End(object sender, EventArgs e)

{

Log.SaveNote(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":Application End!");

//下面的代码是关键，可解决IIS应用程序池自动回收的问题

Thread.Sleep(1000);

//这里设置你的web地址，可以随便指向你的任意一个aspx页面甚至不存在的页面，目的是要激发Application_Start

string url = "http://home.cutepig.net";

HttpWebRequest myHttpWebRequest = (HttpWebRequest)WebRequest.Create(url);

HttpWebResponse myHttpWebResponse = (HttpWebResponse)myHttpWebRequest.GetResponse();

Stream receiveStream = myHttpWebResponse.GetResponseStream();//得到回写的字节流

}

VB.NET代码：

Imports System.Web.SessionState
Imports System.Timers
Imports System.Threading
Imports System.Net
Imports System.Net.WebRequestMethods
Imports System.IO

Public Class Global_asax
    Inherits System.Web.HttpApplication

    Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
        ' 应用程序启动时激发
        Dim SetTime As Integer = 60000   '设定定时时间 单位：秒
        Dim myTimer As System.Timers.Timer = New System.Timers.Timer(SetTime)
        AddHandler myTimer.Elapsed, New ElapsedEventHandler(AddressOf myTimer_Elapsed)
        myTimer.Enabled = True
        myTimer.AutoReset = True
    End Sub

    Sub Session_Start(ByVal sender As Object, ByVal e As EventArgs)
        ' 会话启动时激发
    End Sub

    Sub Application_BeginRequest(ByVal sender As Object, ByVal e As EventArgs)
        ' 每个请求开始时激发
    End Sub

    Sub Application_AuthenticateRequest(ByVal sender As Object, ByVal e As EventArgs)
        ' 尝试验证用户身份时激发
    End Sub

    Sub Application_Error(ByVal sender As Object, ByVal e As EventArgs)
        ' 发生错误时激发
    End Sub

    Sub Session_End(ByVal sender As Object, ByVal e As EventArgs)
        ' 会话结束时激发
    End Sub

    Private Sub myTimer_Elapsed(ByVal source As Object, ByVal e As ElapsedEventArgs)
        Try
             Log.SaveNote(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") & ":AutoTask is Working!")          
            YourTask()
        Catch ee As Exception
             Log.SaveException(ee)
        End Try
    End Sub

    Private Sub YourTask()
        '在这里写你需要执行的任务


    End Sub

    Sub Application_End(ByVal sender As Object, ByVal e As EventArgs)
        ' 应用程序结束时激发
         Log.SaveNote(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") & ":Application End!")        
        Thread.Sleep(1000)
        Dim url As String = "Default.aspx"
        Dim myHttpWebRequest As HttpWebRequest = CType(WebRequest.Create(url), HttpWebRequest)
        Dim myHttpWebResponse As HttpWebResponse = CType(myHttpWebRequest.GetResponse(), HttpWebResponse)
        Dim receiveStream As Stream = myHttpWebResponse.GetResponseStream()
    End Sub

End Class

Imports System.Web.SessionState

Imports System.Timers

Imports System.Threading

Imports System.Net

Imports System.Net.WebRequestMethods

Imports System.IO

Public Class Global_asax

Inherits System.Web.HttpApplication

Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)

' 应用程序启动时激发

Dim SetTime As Integer = 60000 '设定定时时间单位：秒

Dim myTimer As System.Timers.Timer = New System.Timers.Timer(SetTime)

AddHandler myTimer.Elapsed, New ElapsedEventHandler(AddressOf myTimer_Elapsed)

myTimer.Enabled = True

myTimer.AutoReset = True

End Sub

Sub Session_Start(ByVal sender As Object, ByVal e As EventArgs)

' 会话启动时激发

End Sub

Sub Application_BeginRequest(ByVal sender As Object, ByVal e As EventArgs)

' 每个请求开始时激发

End Sub

Sub Application_AuthenticateRequest(ByVal sender As Object, ByVal e As EventArgs)

' 尝试验证用户身份时激发

End Sub

Sub Application_Error(ByVal sender As Object, ByVal e As EventArgs)

' 发生错误时激发

End Sub

Sub Session_End(ByVal sender As Object, ByVal e As EventArgs)

' 会话结束时激发

End Sub

Private Sub myTimer_Elapsed(ByVal source As Object, ByVal e As ElapsedEventArgs)

Try

Log.SaveNote(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") & ":AutoTask is Working!")

YourTask()

Catch ee As Exception

Log.SaveException(ee)

End Try

End Sub

Private Sub YourTask()

'在这里写你需要执行的任务

End Sub

Sub Application_End(ByVal sender As Object, ByVal e As EventArgs)

' 应用程序结束时激发

Log.SaveNote(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") & ":Application End!")

Thread.Sleep(1000)

Dim url As String = "Default.aspx"

Dim myHttpWebRequest As HttpWebRequest = CType(WebRequest.Create(url), HttpWebRequest)

Dim myHttpWebResponse As HttpWebResponse = CType(myHttpWebRequest.GetResponse(), HttpWebResponse)

Dim receiveStream As Stream = myHttpWebResponse.GetResponseStream()

End Sub

End Class

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