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Timer.Timer(TimerCallback, Object, TimeSpan, TimeSpan) Constructor

Initializes a new instance of the Timer class, using TimeSpan values to measure time intervals.

Namespace: System.Threading
Assembly: mscorlib (in mscorlib.dll)

public Timer (
	TimerCallback callback,
	Object state,
	TimeSpan dueTime,
	TimeSpan period
)
public Timer (
	TimerCallback callback, 
	Object state, 
	TimeSpan dueTime, 
	TimeSpan period
)
public function Timer (
	callback : TimerCallback, 
	state : Object, 
	dueTime : TimeSpan, 
	period : TimeSpan
)
Not applicable.

Parameters

callback

A TimerCallback delegate representing a method to be executed.

state

An object containing information to be used by the callback method, or a null reference (Nothing in Visual Basic).

dueTime

The TimeSpan representing the amount of time to delay before the callback parameter invokes its methods. Specify negative one (-1) milliseconds to prevent the timer from starting. Specify zero (0) to start the timer immediately.

period

The time interval between invocations of the methods referenced by callback. Specify negative one (-1) milliseconds to disable periodic signaling.

Exception typeCondition

ArgumentOutOfRangeException

The number of milliseconds in the value of dueTime or period is negative and not equal to Infinite, or is greater than MaxValue.

ArgumentNullException

The callback parameter is a null reference (Nothing in Visual Basic).

The delegate specified by the callback parameter is invoked once after dueTime elapses, and thereafter each time the period time interval elapses.

NoteNote:

Visual Basic users can omit the TimerCallback constructor, and simply use the AddressOf operator when specifying the callback method. Visual Basic automatically calls the correct delegate constructor.

If dueTime is zero (0), callback is invoked immediately. If dueTime is negative one (-1) milliseconds, callback is not invoked; the timer is disabled, but can be re-enabled by calling the Change method.

If period is zero (0) or negative one (-1) milliseconds and dueTime is positive, callback is invoked once; the periodic behavior of the timer is disabled, but can be re-enabled using the Change method.

The method specified for callback should be reentrant, because it is called on ThreadPool threads. The method can be executed simultaneously on two thread pool threads if the timer interval is less than the time required to execute the method, or if all thread pool threads are in use and the method is queued multiple times.

The following code example shows how to create a TimerCallback delegate and initialize a new instance of the Timer class.

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);

        TimeSpan delayTime = new TimeSpan(0, 0, 1);
        TimeSpan intervalTime = new TimeSpan(0, 0, 0, 0, 250);

        // 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, delayTime, intervalTime);

        // When autoEvent signals, change the period to every 
        // 1/2 second.
        autoEvent.WaitOne(5000, false);
        stateTimer.Change(new TimeSpan(0), 
            intervalTime + intervalTime);
        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();
        }
    }
}

import System.*;
import System.Threading.*;
import System.Threading.Thread;

class TimerExample
{
    public static void main(String[] args)
    {
        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);
        TimeSpan delayTime = new TimeSpan(0, 0, 1);
        TimeSpan intervalTime = new TimeSpan(0, 0, 0, 0, 250);

        // 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",
            System.DateTime.get_Now().ToString("h:mm:ss.fff"));

        Timer stateTimer = new Timer(timerDelegate, autoEvent, 
            delayTime, intervalTime);

        // When autoEvent signals, change the period to every 
        // 1/2 second.
        autoEvent.WaitOne(5000, false);
        stateTimer.Change(new TimeSpan(0), intervalTime.Add(intervalTime));
        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.");
    } //main
} //TimerExample

class StatusChecker
{
    private int invokeCount, maxCount;

    public StatusChecker(int count)
    {
        invokeCount = 0;
        maxCount = count;
    } //StatusChecker

    // This method is called by the timer delegate.
    public void CheckStatus(Object stateInfo)
    {
        AutoResetEvent autoEvent = ((AutoResetEvent)(stateInfo));
        Console.WriteLine("{0} Checking status {1,2}.",
            System.DateTime.get_Now().ToString("h:mm:ss.fff"),
            String.valueOf(++invokeCount));
        if (invokeCount == maxCount) {
            // Reset the counter and signal Main.
            invokeCount = 0;
            autoEvent.Set();
        }
    } //CheckStatus
} //StatusChecker

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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