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)
Visual Basic (Declaration)
Public Sub New ( _
callback As TimerCallback, _
state As Object, _
dueTime As Integer, _
period As Integer _
)
Dim callback As TimerCallback
Dim state As Object
Dim dueTime As Integer
Dim period As Integer
Dim instance As New Timer(callback, _
state, dueTime, period)
public Timer(
TimerCallback callback,
Object state,
int dueTime,
int period
)
public:
Timer(
TimerCallback^ callback,
Object^ state,
int dueTime,
int period
)
public function Timer(
callback : TimerCallback,
state : Object,
dueTime : int,
period : int
)
The delegate specified by the callback parameter is invoked once after dueTime elapses, and thereafter each time the period time interval elapses.
vb# Note: |
|---|
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.
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
' 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, 1000, 250)
' When autoEvent signals, change the period to every
' 1/2 second.
autoEvent.WaitOne(5000, False)
stateTimer.Change(0, 500)
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
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();
}
}
}
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 );
// 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,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->~Timer();
Console::WriteLine( "\nDestroying timer." );
}
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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