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ElapsedEventHandler Delegate

Represents the method that will handle the Elapsed event of a Timer.

Namespace:  System.Timers
Assembly:  System (in System.dll)

public delegate void ElapsedEventHandler(
	Object sender,
	ElapsedEventArgs e
)

Parameters

sender
Type: System.Object

The source of the event.

e
Type: System.Timers.ElapsedEventArgs

An ElapsedEventArgs object that contains the event data.

When you create an ElapsedEventHandler delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event handler delegates, see Handling and Raising Events.

The following code example sets up an event handler for the Timer.Elapsed event, creates a timer, and starts the timer. The event handler has the same signature as the ElapsedEventHandler delegate. The event handler displays the SignalTime property each time it is raised.

// Use this code inside a project created with the Visual C# > Windows Desktop > Console Application template.  
// Replace the code in Program.cs with this code.  

using System;

// To avoid confusion with other Timer classes, this sample always uses the fully-qualified 
// name of System.Timers.Timer instead of a using statement for System.Timers. 

public class Example
{
    private static System.Timers.Timer aTimer;

    public static void Main()
    {
        // Normally, the timer is declared at the class level, so that it stays in scope as long as it 
        // is needed. If the timer is declared in a long-running method, KeepAlive must be used to prevent 
        // the JIT compiler from allowing aggressive garbage collection to occur before the method ends. 
        // You can experiment with this by commenting out the class-level declaration and uncommenting  
        // the declaration below; then uncomment the GC.KeepAlive(aTimer) at the end of the method.         
        //System.Timers.Timer aTimer; 

        // Create a timer and set a two second interval.
        aTimer = new System.Timers.Timer();
        aTimer.Interval = 2000;

        // Alternate method: create a Timer with an interval argument to the constructor. 
        //aTimer = new System.Timers.Timer(2000); 

        // Create a timer with a two second interval.
        aTimer = new System.Timers.Timer(2000);

        // Hook up the Elapsed event for the timer. 
        aTimer.Elapsed += OnTimedEvent;

        // Have the timer fire repeated events (true is the default)
        aTimer.AutoReset = true;

        // Start the timer
        aTimer.Enabled = true;

        Console.WriteLine("Press the Enter key to exit the program at any time... ");
        Console.ReadLine();

        // If the timer is declared in a long-running method, use KeepAlive to prevent garbage collection 
        // from occurring before the method ends.  
        //GC.KeepAlive(aTimer) 
    }

    private static void OnTimedEvent(Object source, System.Timers.ElapsedEventArgs e)
    {
        Console.WriteLine("The Elapsed event was raised at {0}", e.SignalTime);
    }
}

// This example displays output like the following:  
//       Press the Enter key to exit the program at any time...  
//       The Elapsed event was raised at 5/20/2015 8:48:58 PM  
//       The Elapsed event was raised at 5/20/2015 8:49:00 PM  
//       The Elapsed event was raised at 5/20/2015 8:49:02 PM  
//       The Elapsed event was raised at 5/20/2015 8:49:04 PM  
//       The Elapsed event was raised at 5/20/2015 8:49:06 PM 

.NET Framework

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

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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