Timers

Timers are lightweight objects that enable you to specify a delegate to be called at a specified time. A thread in the thread pool performs the wait operation.

Using the Timer class is straightforward. You create a Timer, passing a TimerCallback delegate to the callback method, an object representing state that will be passed to the callback, an initial raise time, and a time representing the period between callback invocations. To cancel a pending timer, call the Timer.Dispose function.

Note

There are two other timer classes. The Timer class is a control that works with visual designers and is meant to be used in user interface contexts; it raises events on the user interface thread. The Timer class derives from Component, so it can be used with visual designers; it also raises events, but it raises them on a ThreadPool thread. The Timer class makes callbacks on a ThreadPool thread and does not use the event model at all. It also provides a state object to the callback method, which the other timers do not. It is extremely lightweight.

The following code example starts a timer that starts after one second (1000 milliseconds) and ticks every second until you press the Enter key. The variable containing the reference to the timer is a class-level field, to ensure that the timer is not subject to garbage collection while it is still running. For more information on aggressive garbage collection, see KeepAlive.

using namespace System;
using namespace System::Threading;

public ref class Example
{
private:
    static Timer^ ticker;

public:
    static void TimerMethod(Object^ state)
    {
        Console::Write(".");
    }

    static void Main()
    {
        TimerCallback^ tcb =
           gcnew TimerCallback(&TimerMethod);

        ticker = gcnew Timer(tcb, nullptr, 1000, 1000);

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

int main()
{
    Example::Main();
}

using System;
using System.Threading;

public class Example
{
    private static Timer ticker;

    public static void TimerMethod(object state)
    {
        Console.Write(".");
    }

    public static void Main()
    {
        ticker = new Timer(TimerMethod, null, 1000, 1000);

        Console.WriteLine("Press the Enter key to end the program.");
        Console.ReadLine();
    }
}
Imports System
Imports System.Threading

Public Class Example
    Private Shared ticker As Timer

    Public Shared Sub TimerMethod(state As Object)
        Console.Write(".")
    End Sub

    Public Shared Sub Main()
        ticker = New Timer(AddressOf TimerMethod, Nothing, 1000, 1000)

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

See Also

Timer
Threading Objects and Features