Timer Class

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The Timer component is a server-based timer that raises an Elapsed event in your application after the number of milliseconds in the Interval property has elapsed. You can configure the Timer object to raise the event just once or repeatedly using the AutoReset property. Typically, a Timer object is declared at the class level so that it stays in scope as long as it is needed. You can then handle its Elapsed event to provide regular processing. For example, suppose you have a critical server that must be kept running 24 hours a day, 7 days a week. You could create a service that uses a Timer object to periodically check the server and ensure that the system is up and running. If the system is not responding, the service could attempt to restart the server or notify an administrator.

The Timer class is available in the .NET Framework only. It is not included in the .NET Standard Library and is not available on other platforms, such as .NET Core or the Universal Windows Platform. On these platforms, as well as for portability across all .NET platforms, you should use the System.Threading. Timer class instead.

This type implements the IDisposable interface. When you have finished using the type, you should dispose of it either directly or indirectly. To dispose of the type directly, call its Dispose method in a try /catch block. To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). For more information, see the “Using an Object that Implements IDisposable� section in the IDisposable interface topic.

The server-based System.Timers. Timer class is designed for use with worker threads in a multithreaded environment. Server timers can move among threads to handle the raised Elapsed event, resulting in more accuracy than Windows timers in raising the event on time.

The System.Timers. Timer component raises the Elapsed event, based on the value (in milliseconds) of the Interval property. You can handle this event to perform the processing you need. For example, suppose that you have an online sales application that continuously posts sales orders to a database. The service that compiles the instructions for shipping operates on a batch of orders rather than processing each order individually. You could use a Timer to start the batch processing every 30 minutes.

The System.Timers.Timer class has the same resolution as the system clock. This means that the Elapsed event will fire at an interval defined by the resolution of the system clock if the Interval property is less than the resolution of the system clock. For more information, see the Interval property.

When AutoReset is set to false. a System.Timers. Timer object raises the Elapsed event only once, after the first Interval has elapsed. To keep raising the Elapsed event regularly at the interval defined by the Interval. set AutoReset to true. which is the default value.

The Timer component catches and suppresses all exceptions thrown by event handlers for the Elapsed event. This behavior is subject to change in future releases of the .NET Framework. Note, however, that this is not true of event handlers that execute asynchronously and include the await operator (in C#) or the Await operator (in Visual Basic). Exceptions thrown in these event handlers are propagated back to the calling thread, as the following example illustrates. For more information on exceptions thrown in asynchronous methods, see Exception Handling (Task Parallel Library) .