Export (0) Print
Expand All

Timer Constructor (TimerCallback, Object, TimeSpan, TimeSpan)

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

Namespace:  System.Threading
Assemblies:   mscorlib (in mscorlib.dll)
  System.Threading.Timer (in System.Threading.Timer.dll)

	TimerCallback^ callback, 
	Object^ state, 
	TimeSpan dueTime, 
	TimeSpan period


Type: System.Threading::TimerCallback

A delegate representing a method to be executed.

Type: System::Object

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

Type: System::TimeSpan

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.

Type: System::TimeSpan

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


The number of milliseconds in the value of dueTime or period is negative and not equal to Timeout::Infinite, or is greater than Int32::MaxValue.


The callback parameter is nullptr.

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

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.

Because the Timer class has the same resolution as the system clock, which is approximately 15 milliseconds on Windows 7 and Windows 8 systems, the callback delegate executes at intervals defined by the resolution of the system clock if period is less than the resolution of the system clock. 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 namespace System;
using namespace System::Threading;
ref class StatusChecker
   int invokeCount;
   int maxCount;

   StatusChecker( int count )
      : invokeCount( 0 ), maxCount( count )

   // This method is called by the timer delegate. 
   void CheckStatus( Object^ stateInfo )
      AutoResetEvent^ autoEvent = dynamic_cast<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;


int main()
   AutoResetEvent^ autoEvent = gcnew AutoResetEvent( false );
   StatusChecker^ statusChecker = gcnew StatusChecker( 10 );

   // Create the delegate that invokes methods for the timer.
   TimerCallback^ timerDelegate = gcnew TimerCallback( statusChecker, &StatusChecker::CheckStatus );
   TimeSpan delayTime = TimeSpan(0,0,1);
   TimeSpan intervalTime = 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 = gcnew Timer( timerDelegate,autoEvent,delayTime,intervalTime );

   // When autoEvent signals, change the period to every 1/2 second.
   autoEvent->WaitOne( 5000, false );
   stateTimer->Change( TimeSpan(0), intervalTime + intervalTime );
   Console::WriteLine( "\nChanging period.\n" );

   // When autoEvent signals the second time, dispose of the timer.
   autoEvent->WaitOne( 5000, false );
   Console::WriteLine( "\nDestroying timer." );

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

© 2014 Microsoft