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Timer Constructor (TimerCallback, Object, Int32, Int32)

Initializes a new instance of the Timer class, using a 32-bit signed integer to specify the time interval.

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

public Timer(
	TimerCallback callback,
	Object state,
	int dueTime,
	int period
)

Parameters

callback
Type: System.Threading.TimerCallback

A TimerCallback delegate representing a method to be executed.

state
Type: System.Object

An object containing information to be used by the callback method, or null.

dueTime
Type: System.Int32

The amount of time to delay before callback is invoked, in milliseconds. Specify Timeout.Infinite to prevent the timer from starting. Specify zero (0) to start the timer immediately.

period
Type: System.Int32

The time interval between invocations of callback, in milliseconds. Specify Timeout.Infinite to disable periodic signaling.

ExceptionCondition
ArgumentOutOfRangeException

The dueTime or period parameter is negative and is not equal to Infinite.

ArgumentNullException

The callback parameter is null.

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

[Visual Basic]

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 Timeout.Infinite, callback is not invoked; the timer is disabled, but can be re-enabled by calling the Change method.

If period is zero (0) or Infinite and dueTime is not Infinite, 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()
    {
        // Create an event to signal the timeout count threshold in the 
        // timer callback.
        AutoResetEvent autoEvent     = new AutoResetEvent(false);

        StatusChecker  statusChecker = new StatusChecker(10);

        // Create an inferred delegate that invokes methods for the timer.
        TimerCallback tcb = 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(tcb, 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
{
    private int invokeCount;
    private int  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();
        }
    }
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

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