Timer Class
Implements a timer that raises an event at user-defined intervals. This timer is optimized for use in Windows Forms applications and must be used in a window.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
A Timer is used to raise an event at user-defined intervals. This Windows timer is designed for a single-threaded environment where UI threads are used to perform processing. It requires that the user code have a UI message pump available and always operate from the same thread, or marshal the call onto another thread.
When you use this timer, use the Tick event to perform a polling operation or to display a splash screen for a specified period of time. Whenever the Enabled property is set to true and the Interval property is greater than zero, the Tick event is raised at intervals based on the Interval property setting.
This class provides methods to set the interval, and to start and stop the timer.
Note: |
|---|
The Windows Forms Timer component is single-threaded, and is limited to an accuracy of 55 milliseconds. If you require a multithreaded timer with greater accuracy, use the Timer class in the System.Timers namespace. |
The following example implements a simple interval timer, which sets off an alarm every five seconds. When the alarm occurs, a MessageBox displays a count of the number of times the alarm has started and prompts the user as to whether the timer should continue to run.
Public Class Class1 Private Shared WithEvents myTimer As New System.Windows.Forms.Timer() Private Shared alarmCounter As Integer = 1 Private Shared exitFlag As Boolean = False ' This is the method to run when the timer is raised. Private Shared Sub TimerEventProcessor(ByVal myObject As Object, _ ByVal myEventArgs As EventArgs) _ Handles myTimer.Tick myTimer.Stop() ' Displays a message box asking whether to continue running the timer. If MessageBox.Show("Continue running?", "Count is: " & alarmCounter, _ MessageBoxButtons.YesNo) = DialogResult.Yes Then ' Restarts the timer and increments the counter. alarmCounter += 1 myTimer.Enabled = True Else ' Stops the timer. exitFlag = True End If End Sub Public Shared Sub Main() ' Adds the event and the event handler for the method that will ' process the timer event to the timer. ' Sets the timer interval to 5 seconds. myTimer.Interval = 5000 myTimer.Start() ' Runs the timer, and raises the event. While exitFlag = False ' Processes all the events in the queue. Application.DoEvents() End While End Sub End Class
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
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.
Note: