Windows Service looping - How To?

Question

I have build a windows service using a timer which is not ideal for what i want to do. I have a methord i want to call and as soon as its finnished i want it to start again and again and again. What is the best way of doing this and can you show me an example.

Answer 1

Can you explain a little more what you are trying to accomplish.

When using a timer in a Service you will need to use System.Threading.Timer.

If you are constantly looping then your CPU usage is going to go through the roof. If you are trying to monitor a directory you can use a FileSystemWatcher but this can be troublesome if your host computer is not running Windows. If you are trying to query a table and get results you could have it look every 15 seconds for a new record and if a new record exists mark the function as running via a boolean so that if its still running 15 seconds later it doesn't launch again.

I am going to give you an example of a timer in a system service.

    Private myThreadingTimer As System.Threading.Timer
    Private blnCurrentlyRunning As Boolean = False

    Protected Overrides Sub OnStart(ByVal args() As String)
       Dim myTimerCallback As New TimerCallback(AddressOf OnTimedEvent)
       myThreadingTimer = New System.Threading.Timer(myTimerCallback, Nothing, 1000, 1000)
    End Sub

    Private Sub OnTimedEvent(ByVal state As Object)
        If Date.Now.Second = 1 Or Date.Now.Second = 15 Or Date.Now.Second = 30 Or Date.Now.Second = 45 Then
            If Not blnCurrentlyRunning Then
                blnCurrentlyRunning = True

                Dim myNewThread As New Thread(New ThreadStart(AddressOf MyFunctionIWantToCall))
                myNewThread.Start()
            End If
        End If
    End Sub

Public Sub MyFunctionIWantToCall()
   Try
       'Do Something
   Catch ex As Exception
   Finally
       blnCurrentlyRunning = False
   End Try
End Sub

Answer 2

private AutoResetEvent  m_waitNextExec = new AutoResetEvent(false);
private int m_execTimer = 1000; //Every second
private bool m_isRunning = true;

private void SomeMethod()
{
    while (m_isRunning)
    {
        //Do something

        m_waitNextExec.WaitOne(m_execTimer);
    }   
}

This code gives you more control over the execution of your code. The auto reset event gives you the possibility to reduce the execution rate.

If you want to abort the execution, you just have to do:

m_isRunning = false;
m_waitNextExec.Set();