C#-FORM: System.Threading.Timer and threading issues

[MimiMi]

I want to perform certain tasks at certain intervals (update a GUI). But I also want to be able to update the GUI 'manually' (i.e a button click). How is this best achieved?

I've tried to use a System.Threading.Timer and a TimerCallback, but the problem is that the 'Timer-Tick'-method (that actually performs the GUI update tasks) then executes on a ThreadPool thread, and it seems to exit after a while. I would like the same thread to be alive all the time, and manually be able to access the Timer-Tick-method on that thread as well, when the 'update'-button in the GUI is clicked (timer.Change)..

(Am I making any sense? And is this even possible?)

Part of the tasks performed at certain intervals is ssh-communication, and that's really where the problems arise when the ThreadPool thread exits. Then I get an ssh-exception 'pipe-closed', and I prefer that ssh-session to be up and alive
all the time. I guess I could of course close the ssh-session and re-connect each time the timer ticks, but then the response to the 'update'-click in the GUI would be unacceptedly slow, since my ssh-authorizing takes up to 2 minutes.

Any thoughts or ideas whatsoever? Anyone?

[MimiMi]

I guess the "essence" of this thread could be summed like this:

How to implement a task that is to be automatic as well as invoked by (GUI)-user?
My application (written in C# .NET) is communicating with a remote device through ssh. At certain intervals the application initiates a sequence of commands for the device. I also want to be able to manually perform this "command-sequence" by clicking a button in the gui.

As of now, the command-sequence is performed by using a background thread and a System.Threading.Timer, but the problem is the button click..

Any thoughts or ideas on how this could be implemented?

[kenobewan]

So you want to continue the timer after clicking the button?

[MimiMi]

So you want to continue the timer after clicking the button?

Yes, that is what I want!

[Plater]

Why not just use a windows.forms.timer? you can have an event fire at set intervals and still use the functions it uses?

[MimiMi]

Why not just use a windows.forms.timer? you can have an event fire at set intervals and still use the functions it uses?

Hmmm..I think (don't know though) that it might be a problem since the tasks that are to be performed when the timer ticks are relatively time consuming non-UI processing, and may also raise events for the GUI to update..
In other words, seems bad to me to perform non-UI processing on the thread that controls the user interface..? (I might just be confused here.. but isn't all windows.forms.timer - related code run entirely on the UI-thread?)

[Plater]

Yes you are correct.
I thought maybe all you needed done on the tick interval was checking to see if data had come in on the ssh terminal.

You have a tricky situtation, since you're not supposed to acces UI components outside of the UI thread (it will give you an exception about threadsafe with a bunch of options to fix it)

Could you not create some functions that perform your operations, then have a timer (threading.timer? timers.timer?) that calls those functions on the interval, then you could have your button presses call those functions as well?

[MimiMi]

Could you not create some functions that perform your operations, then have a timer (threading.timer? timers.timer?) that calls those functions on the interval, then you could have your button presses call those functions as well?

Seems like the most simple and straightforward way to do it, yes.

I think the main problem I've been having is keeping the ssh-session alive all the time, AND accessing that ssh-session from another thread than the one it runs on when performing the operations.. and that's probably what's been making me try to "do everything on the same thread".. (and hence making it all quite difficult)

So, the solution is probably to have a background thread alive all the time (the ssh-session) and have another thread (timer) run the functions that perform my operations at certain intervals, and have yet another thread run the functions when the gui button is pressed.

I just need to figure out how to access the ssh-session from other threads than the one it runs on.

Even though I'm far from having it all solved, I think your replies have helped me (think in different ways), so for that I'm really grateful! Thanks!

[Plater]

Make the SSh object public?

[balabaster]

This seems like a task for a delegate...I would create a method that does the work and embed that in my form...such that (bear in mind that the code I've written below is conceptual - I've not tested it so you really need to understand what it's supposed to do rather than just dropping it into your code):

'Declaring your SSH object here means you can open it on your main 
'thread and keep updating it from your timer as well as from your main form via 
'the RunTheTask method.
Private MySSHObject As Object 'Whatever it is
 
'This delegate basically gives us the ability to pass a method address between
'routines rather than a value.  We can use this method to keep invoking the
'delegate until InvokeRequired is no longer true, at which point our code will run.
Private Delegate Sub RunTheTaskDelegate(<Add any parameters you require in here>)
 
'This is the RunTheTask method that really does all the work.  Any requirement 
'to send data via the SSH object should go through the RunTheTask.  Any 
'parameters you specify in the parenthesis her must also be applied to the 
'delegate sub above and vice versa.  Basically interpreted, the method 
'signatures of your main method and your delegate need to match.
Private Sub RunTheTask(<Add any parameters you require in here>)
  If Me.InvokeRequired Then
    Me.Invoke(New RunTheTaskDelegate(AddressOf RunTheTask), <Add all your parameters from your header here, comma separate them>)
  Else
    'This is where the rest of your code goes
    'Check SSH is connected, if not, connect it
    'Run the code...
  End If
End Sub
 
'Timer elapsed event
Private Sub Timer_Elapsed(Blah blah blah...) Handles MyTimer.Elapsed
  RunTheTask
End Sub
 
Private Sub Button_Clicked(Blah blah blah...) Handles MyButton.Clicked
  RunTheTask
End Sub

This is the same way you run any task within your form from multiple threads...you could equally call the RunTheTask method from a self created thread.

Obviously this would need to be translated to C# ;) The concepts are all identical though.

public delegate void MyDelegate(string MyParam1)
 
public void MySub(string MyParam1)
{
  if (this.InvokeRequired) {
    this.invoke(new MyDelegate(MySub), MyParam1);
  else {
    //Do stuff
  }
} 

Hope that provides some insight...