Timer Timer Timer Timer Constructors

Definition

Overloads

Timer(TimerCallback) Timer(TimerCallback) Timer(TimerCallback) Timer(TimerCallback)

Initializes a new instance of the Timer class with an infinite period and an infinite due time, using the newly created Timer object as the state object.

Timer(TimerCallback, Object, Int32, Int32) Timer(TimerCallback, Object, Int32, Int32) Timer(TimerCallback, Object, Int32, Int32) Timer(TimerCallback, Object, Int32, Int32)

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

Timer(TimerCallback, Object, Int64, Int64) Timer(TimerCallback, Object, Int64, Int64) Timer(TimerCallback, Object, Int64, Int64) Timer(TimerCallback, Object, Int64, Int64)

Initializes a new instance of the Timer class, using 64-bit signed integers to measure time intervals.

Timer(TimerCallback, Object, TimeSpan, TimeSpan) Timer(TimerCallback, Object, TimeSpan, TimeSpan) Timer(TimerCallback, Object, TimeSpan, TimeSpan) Timer(TimerCallback, Object, TimeSpan, TimeSpan)

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

Timer(TimerCallback, Object, UInt32, UInt32) Timer(TimerCallback, Object, UInt32, UInt32) Timer(TimerCallback, Object, UInt32, UInt32) Timer(TimerCallback, Object, UInt32, UInt32)

Initializes a new instance of the Timer class, using 32-bit unsigned integers to measure time intervals.

Timer(TimerCallback) Timer(TimerCallback) Timer(TimerCallback) Timer(TimerCallback)

Initializes a new instance of the Timer class with an infinite period and an infinite due time, using the newly created Timer object as the state object.

public:
 Timer(System::Threading::TimerCallback ^ callback);
public Timer (System.Threading.TimerCallback callback);
new System.Threading.Timer : System.Threading.TimerCallback -> System.Threading.Timer
Public Sub New (callback As TimerCallback)

Parameters

callback
TimerCallback TimerCallback TimerCallback TimerCallback

A TimerCallback delegate representing a method to be executed.

Examples

The following code example creates a new timer, using the timer itself as the state object. The Change method is used to start the timer. When the timer callback occurs, the state object is used to turn the timer off.

using System;
using System.Threading;

public class Example
{
    public static void Main()
    {
        // Create an instance of the Example class, and start two
        // timers.
        Example ex = new Example();
        ex.StartTimer(2000);
        ex.StartTimer(1000);

        Console.WriteLine("Press Enter to end the program.");
        Console.ReadLine();
    }

    public void StartTimer(int dueTime)
    {
        Timer t = new Timer(new TimerCallback(TimerProc));
        t.Change(dueTime, 0);
    }

    private void TimerProc(object state)
    {
        // The state object is the Timer object.
        Timer t = (Timer) state;
        t.Dispose();
        Console.WriteLine("The timer callback executes.");
    }
}
Imports System
Imports System.Threading

Public Class Example
    Public Shared Sub Main()
        ' Create an instance of the Example class, and start two
        ' timers.
        Dim ex As New Example()
        ex.StartTimer(2000)
        ex.StartTimer(1000)

        Console.WriteLine("Press Enter to end the program.")
        Console.ReadLine()
    End Sub

    Public Sub StartTimer(ByVal dueTime As Integer)
        Dim t As New Timer(AddressOf TimerProc)
        t.Change(dueTime, 0)
    End Sub

    Private Sub TimerProc(ByVal state As Object)
        ' The state object is the Timer object.
        Dim t As Timer = CType(state, Timer)
        t.Dispose()
        Console.WriteLine("The timer callback executes.")
    End Sub
End Class

Remarks

Call this constructor when you want to use the Timer object itself as the state object. After creating the timer, use the Change method to set the interval and due time.

This constructor specifies an infinite due time before the first callback and an infinite interval between callbacks, in order to prevent the first callback from occurring before the Timer object is assigned to the state object.

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.

Timer(TimerCallback, Object, Int32, Int32) Timer(TimerCallback, Object, Int32, Int32) Timer(TimerCallback, Object, Int32, Int32) Timer(TimerCallback, Object, Int32, Int32)

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

public:
 Timer(System::Threading::TimerCallback ^ callback, System::Object ^ state, int dueTime, int period);
public Timer (System.Threading.TimerCallback callback, object state, int dueTime, int period);
new System.Threading.Timer : System.Threading.TimerCallback * obj * int * int -> System.Threading.Timer
Public Sub New (callback As TimerCallback, state As Object, dueTime As Integer, period As Integer)

Parameters

callback
TimerCallback TimerCallback TimerCallback TimerCallback

A TimerCallback delegate representing a method to be executed.

state
Object Object Object Object

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

dueTime
Int32 Int32 Int32 Int32

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

period
Int32 Int32 Int32 Int32

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

Exceptions

Examples

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
{
private:
    int invokeCount, maxCount;

public:
    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:h:mm:ss.fff} Checking status {1,2}.",
                           DateTime::Now, ++invokeCount);

        if (invokeCount == maxCount) {
            // Reset the counter and signal the waiting thread.
            invokeCount  = 0;
            autoEvent->Set();
        }
    }
};

ref class TimerExample
{
public:
    static void Main()
    {
        // Create an AutoResetEvent to signal the timeout threshold in the
        // timer callback has been reached.
        AutoResetEvent^ autoEvent = gcnew AutoResetEvent(false);

        StatusChecker^ statusChecker = gcnew StatusChecker(10);

        // Create a delegate that invokes methods for the timer.
        TimerCallback^ tcb =
           gcnew TimerCallback(statusChecker, &StatusChecker::CheckStatus);

        // Create a timer that invokes CheckStatus after one second, 
        // and every 1/4 second thereafter.
        Console::WriteLine("{0:h:mm:ss.fff} Creating timer.\n",
                           DateTime::Now);
        Timer^ stateTimer = gcnew Timer(tcb, autoEvent, 1000, 250);

        // When autoEvent signals, change the period to every half second.
        autoEvent->WaitOne(5000, false);
        stateTimer->Change(0, 500);
        Console::WriteLine("\nChanging period to .5 seconds.\n");

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

int main()
{
    TimerExample::Main();
}
// The example displays output like the following:
//       11:59:54.202 Creating timer.
//       
//       11:59:55.217 Checking status  1.
//       11:59:55.466 Checking status  2.
//       11:59:55.716 Checking status  3.
//       11:59:55.968 Checking status  4.
//       11:59:56.218 Checking status  5.
//       11:59:56.470 Checking status  6.
//       11:59:56.722 Checking status  7.
//       11:59:56.972 Checking status  8.
//       11:59:57.223 Checking status  9.
//       11:59:57.473 Checking status 10.
//       
//       Changing period to .5 seconds.
//       
//       11:59:57.474 Checking status  1.
//       11:59:57.976 Checking status  2.
//       11:59:58.476 Checking status  3.
//       11:59:58.977 Checking status  4.
//       11:59:59.477 Checking status  5.
//       11:59:59.977 Checking status  6.
//       12:00:00.478 Checking status  7.
//       12:00:00.980 Checking status  8.
//       12:00:01.481 Checking status  9.
//       12:00:01.981 Checking status 10.
//       
//       Destroying timer.
using System;
using System.Threading;

class TimerExample
{
    static void Main()
    {
        // Create an AutoResetEvent to signal the timeout threshold in the
        // timer callback has been reached.
        var autoEvent = new AutoResetEvent(false);
        
        var statusChecker = new StatusChecker(10);

        // Create a timer that invokes CheckStatus after one second, 
        // and every 1/4 second thereafter.
        Console.WriteLine("{0:h:mm:ss.fff} Creating timer.\n", 
                          DateTime.Now);
        var stateTimer = new Timer(statusChecker.CheckStatus, 
                                   autoEvent, 1000, 250);

        // When autoEvent signals, change the period to every half second.
        autoEvent.WaitOne();
        stateTimer.Change(0, 500);
        Console.WriteLine("\nChanging period to .5 seconds.\n");

        // When autoEvent signals the second time, dispose of the timer.
        autoEvent.WaitOne();
        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 the waiting thread.
            invokeCount = 0;
            autoEvent.Set();
        }
    }
}
// The example displays output like the following:
//       11:59:54.202 Creating timer.
//       
//       11:59:55.217 Checking status  1.
//       11:59:55.466 Checking status  2.
//       11:59:55.716 Checking status  3.
//       11:59:55.968 Checking status  4.
//       11:59:56.218 Checking status  5.
//       11:59:56.470 Checking status  6.
//       11:59:56.722 Checking status  7.
//       11:59:56.972 Checking status  8.
//       11:59:57.223 Checking status  9.
//       11:59:57.473 Checking status 10.
//       
//       Changing period to .5 seconds.
//       
//       11:59:57.474 Checking status  1.
//       11:59:57.976 Checking status  2.
//       11:59:58.476 Checking status  3.
//       11:59:58.977 Checking status  4.
//       11:59:59.477 Checking status  5.
//       11:59:59.977 Checking status  6.
//       12:00:00.478 Checking status  7.
//       12:00:00.980 Checking status  8.
//       12:00:01.481 Checking status  9.
//       12:00:01.981 Checking status 10.
//       
//       Destroying timer.
Imports System.Threading

Public Module Example
    Public Sub Main()
        ' Use an AutoResetEvent to signal the timeout threshold in the
        ' timer callback has been reached.
        Dim autoEvent As New AutoResetEvent(False)

        Dim statusChecker As New StatusChecker(10)

        ' Create a timer that invokes CheckStatus after one second, 
        ' and every 1/4 second thereafter.
        Console.WriteLine("{0:h:mm:ss.fff} Creating timer." & vbCrLf, 
                          DateTime.Now)
        Dim stateTimer As New Timer(AddressOf statusChecker.CheckStatus, 
                                    autoEvent, 1000, 250)

        ' When autoEvent signals, change the period to every half second.
        autoEvent.WaitOne()
        stateTimer.Change(0, 500)
        Console.WriteLine(vbCrLf & "Changing period to .5 seconds." & vbCrLf)

        ' When autoEvent signals the second time, dispose of the timer.
        autoEvent.WaitOne()
        stateTimer.Dispose()
        Console.WriteLine(vbCrLf & "Destroying timer.")
    End Sub
End Module

Public Class StatusChecker
    Dim invokeCount, maxCount As Integer 

    Sub New(count As Integer)
        invokeCount  = 0
        maxCount = count
    End Sub

    ' The timer callback method.
    Sub CheckStatus(stateInfo As Object)
        Dim autoEvent As AutoResetEvent = DirectCast(stateInfo, AutoResetEvent)
        invokeCount += 1
        Console.WriteLine("{0:h:mm:ss.fff} Checking status {1,2}.", 
                          DateTime.Now, invokeCount)
        If invokeCount = maxCount Then
            ' Reset the counter and signal the waiting thread.
            invokeCount = 0
            autoEvent.Set()
        End If
    End Sub
End Class
' The example displays output like the following:
'       11:59:54.202 Creating timer.
'       
'       11:59:55.217 Checking status  1.
'       11:59:55.466 Checking status  2.
'       11:59:55.716 Checking status  3.
'       11:59:55.968 Checking status  4.
'       11:59:56.218 Checking status  5.
'       11:59:56.470 Checking status  6.
'       11:59:56.722 Checking status  7.
'       11:59:56.972 Checking status  8.
'       11:59:57.223 Checking status  9.
'       11:59:57.473 Checking status 10.
'       
'       Changing period to .5 seconds.
'       
'       11:59:57.474 Checking status  1.
'       11:59:57.976 Checking status  2.
'       11:59:58.476 Checking status  3.
'       11:59:58.977 Checking status  4.
'       11:59:59.477 Checking status  5.
'       11:59:59.977 Checking status  6.
'       12:00:00.478 Checking status  7.
'       12:00:00.980 Checking status  8.
'       12:00:01.481 Checking status  9.
'       12:00:01.981 Checking status 10.
'       
'       Destroying timer.

Remarks

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 Timeout.Infinite, 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 Timeout.Infinite and dueTime is not Timeout.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.

See also

Timer(TimerCallback, Object, Int64, Int64) Timer(TimerCallback, Object, Int64, Int64) Timer(TimerCallback, Object, Int64, Int64) Timer(TimerCallback, Object, Int64, Int64)

Initializes a new instance of the Timer class, using 64-bit signed integers to measure time intervals.

public:
 Timer(System::Threading::TimerCallback ^ callback, System::Object ^ state, long dueTime, long period);
public Timer (System.Threading.TimerCallback callback, object state, long dueTime, long period);
new System.Threading.Timer : System.Threading.TimerCallback * obj * int64 * int64 -> System.Threading.Timer
Public Sub New (callback As TimerCallback, state As Object, dueTime As Long, period As Long)

Parameters

callback
TimerCallback TimerCallback TimerCallback TimerCallback

A TimerCallback delegate representing a method to be executed.

state
Object Object Object Object

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

dueTime
Int64 Int64 Int64 Int64

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

period
Int64 Int64 Int64 Int64

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

Exceptions

The dueTime or period parameter is greater than 4294967294.

Remarks

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 Timeout.Infinite, 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 Timeout.Infinite and dueTime is not Timeout.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.

See also

Timer(TimerCallback, Object, TimeSpan, TimeSpan) Timer(TimerCallback, Object, TimeSpan, TimeSpan) Timer(TimerCallback, Object, TimeSpan, TimeSpan) Timer(TimerCallback, Object, TimeSpan, TimeSpan)

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

public:
 Timer(System::Threading::TimerCallback ^ callback, System::Object ^ state, TimeSpan dueTime, TimeSpan period);
public Timer (System.Threading.TimerCallback callback, object state, TimeSpan dueTime, TimeSpan period);
new System.Threading.Timer : System.Threading.TimerCallback * obj * TimeSpan * TimeSpan -> System.Threading.Timer
Public Sub New (callback As TimerCallback, state As Object, dueTime As TimeSpan, period As TimeSpan)

Parameters

callback
TimerCallback TimerCallback TimerCallback TimerCallback

A delegate representing a method to be executed.

state
Object Object Object Object

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

dueTime
TimeSpan TimeSpan TimeSpan 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.

period
TimeSpan TimeSpan TimeSpan TimeSpan

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

Exceptions

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

Examples

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
{
private:
   int invokeCount;
   int maxCount;

public:
   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;
         autoEvent->Set();
      }
   }

};

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 );
   stateTimer->~Timer();
   Console::WriteLine( "\nDestroying timer." );
}

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();
        }
    }
}
Imports Microsoft.VisualBasic
Imports System
Imports System.Threading

Public Class TimerExample

    <MTAThread> _
    Shared Sub Main()
    
        Dim autoEvent As New AutoResetEvent(False)
        Dim statusChecker As New StatusChecker(10)

        ' Create the delegate that invokes methods for the timer.
        Dim timerDelegate As TimerCallback = _
            AddressOf statusChecker.CheckStatus

        Dim delayTime As New TimeSpan(0, 0, 1)
        Dim intervalTime As 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." & vbCrLf, _
            DateTime.Now.ToString("h:mm:ss.fff"))
        Dim stateTimer As Timer = 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(vbCrLf & "Changing period." & vbCrLf)

        ' When autoEvent signals the second time, dispose of 
        ' the timer.
        autoEvent.WaitOne(5000, False)
        stateTimer.Dispose()
        Console.WriteLine(vbCrLf & "Destroying timer.")
    
    End Sub
End Class

Public Class StatusChecker

    Dim invokeCount, maxCount As Integer 

    Sub New(count As Integer)
        invokeCount  = 0
        maxCount = count
    End Sub

    ' This method is called by the timer delegate.
    Sub CheckStatus(stateInfo As Object)
        Dim autoEvent As AutoResetEvent = _
            DirectCast(stateInfo, AutoResetEvent)
        invokeCount += 1
        Console.WriteLine("{0} Checking status {1,2}.", _
            DateTime.Now.ToString("h:mm:ss.fff"), _
            invokeCount.ToString())

        If invokeCount = maxCount Then
        
            ' Reset the counter and signal to stop the timer.
            invokeCount  = 0
            autoEvent.Set()
        End If
    End Sub

End Class

Remarks

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.

See also

Timer(TimerCallback, Object, UInt32, UInt32) Timer(TimerCallback, Object, UInt32, UInt32) Timer(TimerCallback, Object, UInt32, UInt32) Timer(TimerCallback, Object, UInt32, UInt32)

Important

This API is not CLS-compliant.

Initializes a new instance of the Timer class, using 32-bit unsigned integers to measure time intervals.

public:
 Timer(System::Threading::TimerCallback ^ callback, System::Object ^ state, System::UInt32 dueTime, System::UInt32 period);
[System.CLSCompliant(false)]
public Timer (System.Threading.TimerCallback callback, object state, uint dueTime, uint period);
new System.Threading.Timer : System.Threading.TimerCallback * obj * uint32 * uint32 -> System.Threading.Timer
Public Sub New (callback As TimerCallback, state As Object, dueTime As UInteger, period As UInteger)

Parameters

callback
TimerCallback TimerCallback TimerCallback TimerCallback

A delegate representing a method to be executed.

state
Object Object Object Object

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

dueTime
UInt32 UInt32 UInt32 UInt32

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

period
UInt32 UInt32 UInt32 UInt32

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

Exceptions

Remarks

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 Timeout.Infinite, 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 Timeout.Infinite and dueTime is not Timeout.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.

See also

Applies to