我需要创建一些Windows服务,每过N段时间就会执行。
问题是:
我应该使用哪个计时器控件:System.Timers.Timer
还是System.Threading.Timer
?这会对什么产生影响吗?
我之所以问是因为我听到了很多关于System.Timers.Timer
在Windows服务中无法正确工作的证据。
谢谢。
我需要创建一些Windows服务,每过N段时间就会执行。
问题是:
我应该使用哪个计时器控件:System.Timers.Timer
还是System.Threading.Timer
?这会对什么产生影响吗?
我之所以问是因为我听到了很多关于System.Timers.Timer
在Windows服务中无法正确工作的证据。
谢谢。
无论是System.Timers.Timer
还是System.Threading.Timer
都适用于服务。
你应该避免使用的计时器是System.Web.UI.Timer
和System.Windows.Forms.Timer
,它们分别用于ASP应用程序和WinForms。使用它们会导致服务加载一个不真正需要的附加程序集。
请像以下示例一样使用System.Timers.Timer
(同时,请确保使用类级别变量来防止垃圾回收,如Tim Robinson的答案中所述):
using System;
using System.Timers;
public class Timer1
{
private static System.Timers.Timer aTimer;
public static void Main()
{
// Normally, the timer is declared at the class level,
// so that it stays in scope as long as it is needed.
// If the timer is declared in a long-running method,
// KeepAlive must be used to prevent the JIT compiler
// from allowing aggressive garbage collection to occur
// before the method ends. (See end of method.)
//System.Timers.Timer aTimer;
// Create a timer with a ten second interval.
aTimer = new System.Timers.Timer(10000);
// Hook up the Elapsed event for the timer.
aTimer.Elapsed += new ElapsedEventHandler(OnTimedEvent);
// Set the Interval to 2 seconds (2000 milliseconds).
aTimer.Interval = 2000;
aTimer.Enabled = true;
Console.WriteLine("Press the Enter key to exit the program.");
Console.ReadLine();
// If the timer is declared in a long-running method, use
// KeepAlive to prevent garbage collection from occurring
// before the method ends.
//GC.KeepAlive(aTimer);
}
// Specify what you want to happen when the Elapsed event is
// raised.
private static void OnTimedEvent(object source, ElapsedEventArgs e)
{
Console.WriteLine("The Elapsed event was raised at {0}", e.SignalTime);
}
}
/* This code example produces output similar to the following:
Press the Enter key to exit the program.
The Elapsed event was raised at 5/20/2007 8:42:27 PM
The Elapsed event was raised at 5/20/2007 8:42:29 PM
The Elapsed event was raised at 5/20/2007 8:42:31 PM
...
*/
如果您选择使用 System.Threading.Timer
,您可以按如下方式使用它:using System;
using System.Threading;
class TimerExample
{
static void Main()
{
AutoResetEvent autoEvent = new AutoResetEvent(false);
StatusChecker statusChecker = new StatusChecker(10);
// Create the delegate that invokes methods for the timer.
TimerCallback timerDelegate =
new TimerCallback(statusChecker.CheckStatus);
// Create a timer that signals the delegate to invoke
// CheckStatus after one second, and every 1/4 second
// thereafter.
Console.WriteLine("{0} Creating timer.\n",
DateTime.Now.ToString("h:mm:ss.fff"));
Timer stateTimer =
new Timer(timerDelegate, autoEvent, 1000, 250);
// When autoEvent signals, change the period to every
// 1/2 second.
autoEvent.WaitOne(5000, false);
stateTimer.Change(0, 500);
Console.WriteLine("\nChanging period.\n");
// When autoEvent signals the second time, dispose of
// the timer.
autoEvent.WaitOne(5000, false);
stateTimer.Dispose();
Console.WriteLine("\nDestroying timer.");
}
}
class StatusChecker
{
int invokeCount, maxCount;
public StatusChecker(int count)
{
invokeCount = 0;
maxCount = count;
}
// This method is called by the timer delegate.
public void CheckStatus(Object stateInfo)
{
AutoResetEvent autoEvent = (AutoResetEvent)stateInfo;
Console.WriteLine("{0} Checking status {1,2}.",
DateTime.Now.ToString("h:mm:ss.fff"),
(++invokeCount).ToString());
if(invokeCount == maxCount)
{
// Reset the counter and signal Main.
invokeCount = 0;
autoEvent.Set();
}
}
}
这两个例子都来自于MSDN页面。
"如果你正在编写一个运行计时器的Windows服务,你应该重新评估你的解决方案。"
–Jon Galloway,ASP.NET MVC社区项目经理,作者,兼职超级英雄
任何一种都可以正常工作。实际上,System.Threading.Timer在内部使用了System.Timers.Timer。
话虽如此,不正确地使用System.Timers.Timer很容易。如果您没有在某个变量中存储Timer对象,那么它可能会被垃圾回收。如果发生这种情况,您的计时器将不再触发。调用Dispose方法停止计时器,或使用System.Threading.Timer类,它是一个稍微更好的封装。
到目前为止,您遇到了哪些问题?
System.Timers.Timer
,因为它无法处理抛出的异常。 - Malachi我同意前面的评论,最好考虑一种不同的方法。我的建议是编写一个控制台应用程序并使用Windows计划任务程序:
这将会:
System.Threading.Timer
和System.Timers.Timer
都可以工作。两者之间的主要区别在于System.Threading.Timer
是对另一个计时器的包装。
这在过去给我带来了很大的问题,因此我总是使用"System.Threading.Timer"并且仍然非常好地处理您的异常。
System.Threading.Timer
会有更多的异常处理,而System.Timers.Timer
将吞噬所有异常。
我知道这个帖子有点老了,但它对我有用,我认为值得注意的是还有另一个原因为什么System.Threading.Timer
可能是一个好的方法。
当您需要定期执行可能需要很长时间的作业,并且希望确保在作业之间使用整个等待期间,或者如果您不希望在作业花费的时间超过计时器周期的情况下再次运行作业。
您可以使用以下内容:
using System;
using System.ServiceProcess;
using System.Threading;
public partial class TimerExampleService : ServiceBase
{
private AutoResetEvent AutoEventInstance { get; set; }
private StatusChecker StatusCheckerInstance { get; set; }
private Timer StateTimer { get; set; }
public int TimerInterval { get; set; }
public CaseIndexingService()
{
InitializeComponent();
TimerInterval = 300000;
}
protected override void OnStart(string[] args)
{
AutoEventInstance = new AutoResetEvent(false);
StatusCheckerInstance = new StatusChecker();
// Create the delegate that invokes methods for the timer.
TimerCallback timerDelegate =
new TimerCallback(StatusCheckerInstance.CheckStatus);
// Create a timer that signals the delegate to invoke
// 1.CheckStatus immediately,
// 2.Wait until the job is finished,
// 3.then wait 5 minutes before executing again.
// 4.Repeat from point 2.
Console.WriteLine("{0} Creating timer.\n",
DateTime.Now.ToString("h:mm:ss.fff"));
//Start Immediately but don't run again.
StateTimer = new Timer(timerDelegate, AutoEventInstance, 0, Timeout.Infinite);
while (StateTimer != null)
{
//Wait until the job is done
AutoEventInstance.WaitOne();
//Wait for 5 minutes before starting the job again.
StateTimer.Change(TimerInterval, Timeout.Infinite);
}
//If the Job somehow takes longer than 5 minutes to complete then it wont matter because we will always wait another 5 minutes before running again.
}
protected override void OnStop()
{
StateTimer.Dispose();
}
}
class StatusChecker
{
public StatusChecker()
{
}
// This method is called by the timer delegate.
public void CheckStatus(Object stateInfo)
{
AutoResetEvent autoEvent = (AutoResetEvent)stateInfo;
Console.WriteLine("{0} Start Checking status.",
DateTime.Now.ToString("h:mm:ss.fff"));
//This job takes time to run. For example purposes, I put a delay in here.
int milliseconds = 5000;
Thread.Sleep(milliseconds);
//Job is now done running and the timer can now be reset to wait for the next interval
Console.WriteLine("{0} Done Checking status.",
DateTime.Now.ToString("h:mm:ss.fff"));
autoEvent.Set();
}
}