Re: [Nplot-devel] Real-Time charting

[Dave C. <dav...@gm...>]

MT,

Cross thread UI interaction is a big headache I've found.

I've since moved from using the Form thread timer to a
System.Threading.Timer. This way I can have an intermediate object
receive events from the environment (tick server) and then build OHLC
bars there. A form (or whatever object that needs to consume bars - 1
second, 5 second, 1 minute, etc.) requests a certain periodicity from
the barbuilder object. This object then creates a Threading timer
which emits bars at the specified interval. The form then consumes
those events, saves the bars in a cache (datatable) and on that event
repaints the graph.

The problem of course is that this object's Threading timer thread is
cross threaded from the form. And so I must perform a
this.InvokeRequired test and use that method delegate:

if (this.InvokeRequired) {
  this.Invoke(new MethodInvoker(ProcessLatestQuote));
  return;
}

Even so, I'm getting what appear to be cross thread lockups at update
frequencies of 2 seconds or less. So I'm thinking that in order to
avoid these lockups I must do nothing aside from update a local cache
of quotes on the Threading timer event - and get out fast.

And then to lock(cache) {} while I perform a graph update.

Sorry if this appears off-topic for this list. But the concept of
graph updates on timers and cross threading is an issue that many will
encounter when using NPlot to graph real time data.

Regards,
Dave Cline

On Thu, Mar 13, 2008 at 6:44 AM, MT <mt...@ya...> wrote:
> Thanks Dave,
>
>  That example worked great for me.  My mistake was to use System.Timers.Timer instead of Windows.Forms.Timer.  System.Timers.Timer executes on an arbitrary thread which was the source of my problem I think.
>



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