Timer::Change Method (TimeSpan, TimeSpan)

 

Changes the start time and the interval between method invocations for a timer, using TimeSpan values to measure time intervals.

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

public:
bool Change(
	TimeSpan dueTime,
	TimeSpan period
)

Parameters

dueTime
Type: System::TimeSpan

A TimeSpan representing the amount of time to delay before invoking the callback method specified when the Timer was constructed. Specify negative one (-1) milliseconds to prevent the timer from restarting. Specify zero (0) to restart the timer immediately.

period
Type: System::TimeSpan

The time interval between invocations of the callback method specified when the Timer was constructed. Specify negative one (-1) milliseconds to disable periodic signaling.

Return Value

Type: System::Boolean

true if the timer was successfully updated; otherwise, false.

Exception Condition
ObjectDisposedException

The Timer has already been disposed.

ArgumentOutOfRangeException

The dueTime or period parameter, in milliseconds, is less than -1.

NotSupportedException

The dueTime or period parameter, in milliseconds, is greater than 4294967294.

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

If dueTime is zero (0), the callback method is invoked immediately. If dueTime is negative one (-1) milliseconds, the callback method is never invoked; the timer is disabled, but can be re-enabled by calling Change and specifying a positive value for dueTime.

If period is zero (0) or negative one (-1) milliseconds, and dueTime is positive, the callback method is invoked once; the periodic behavior of the timer is disabled, but can be re-enabled by calling Change and specifying a value greater than zero for period.

The Change method can be called from the TimerCallback delegate.

The following code example demonstrates how to start a Timer and, after a set number of invocations, change its period.

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." );
}

Universal Windows Platform
Available since 8.1
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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