Timer Constructor (TimerCallback)

Parameters

• callback
  Type: System.Threading.TimerCallback
  A delegate that represents a method to be executed.

Imports System.Threading

Public Class Example

    Private Shared outputBlock As System.Windows.Controls.TextBlock

    Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
        Example.outputBlock = outputBlock
        outputBlock.Text &= "Refresh the page to run the example again." & vbLf

        ' Create an instance of the Example class, and start two
        ' timers.
        Dim ex As New Example()
        ex.StartTimer(2000)
        ex.StartTimer(1000)
    End Sub

    Public Sub StartTimer(ByVal dueTime As Integer)
        Dim t As New Timer(AddressOf TimerProc)
        t.Change(dueTime, 0)
    End Sub

    ' The callback method is invoked on a ThreadPool thread by the Timer. In 
    ' order to update the TextBlock object, which is on the UI thread, you must 
    ' make the cross-thread call by using the Dispatcher object that is 
    ' associated with the TextBlock.
    Private Sub TimerProc(ByVal state As Object)
        ' The state object is the Timer object.
        Dim t As Timer = CType(state, Timer)
        t.Dispose()

        Example.outputBlock.Dispatcher.BeginInvoke(displayHelper, _
                                                   "Timer callback executes." & vbLf)
    End Sub

    ' The DisplayOutput helper method and its delegate, displayHelper, are used by
    ' the BeginInvoke method of the Dispatcher object.
    Private Shared displayHelper As New Action(Of String)(AddressOf DisplayOutput)
    Private Shared Sub DisplayOutput(ByVal msg As String)
        Example.outputBlock.Text &= msg
    End Sub

End Class

' This example produces the following output:
'
'Refresh the page to run the example again.
'Timer callback executes.
'Timer callback executes.

using System;
using System.Threading;

public class Example
{
    private static System.Windows.Controls.TextBlock outputBlock;

    public static void Demo(System.Windows.Controls.TextBlock outputBlock)
    {
        Example.outputBlock = outputBlock;
        outputBlock.Text += "Refresh the page to run the example again.\n";

        // Create an instance of the Example class, and start two
        // timers.
        Example ex = new Example();
        ex.StartTimer(2000);
        ex.StartTimer(1000);
    }

    public void StartTimer(int dueTime)
    {
        Timer t = new Timer(TimerProc);
        t.Change(dueTime, 0);
    }

    // The callback method is invoked on a ThreadPool thread by the Timer. In 
    // order to update the TextBlock object, which is on the UI thread, you must 
    // make the cross-thread call by using the Dispatcher object that is 
    // associated with the TextBlock.
    private void TimerProc(object state)
    {
        // The state object is the Timer object.
        Timer t = (Timer) state;
        t.Dispose();

        Example.outputBlock.Dispatcher.BeginInvoke(delegate () { 
               Example.outputBlock.Text += "Timer callback executes.\n"; });
    }
}

/* This example produces the following output:

Refresh the page to run the example again.
Timer callback executes.
Timer callback executes.
 */