timer/threading

[RobcPettit@yahoo.co.uk]

Hi, Im using a timer every 1 second to update a datagridview, but Im
haveing problems getting it to run on a seperate thread. At the moment
the form freezes when the thread runs, I think its because im firing
the thread with in the timer, Ive tried fireing the timer from thread
start. This is my trimmed code;
private void timer1_Tick(obj ect sender, EventArgs e)
{
Thread thread = new Thread(new ThreadStart(liv eprices));
thread.IsBackgr ound = true;
thread.Start();
}
public delegate void onliveprices();
private void liveprices()
{
if (InvokeRequired )
{
BeginInvoke(new onliveprices(li veprices));
}
else
{
dowork
puts data into dateset and adds new rows to table
adds table to datagridview

}
}

I need to run liveprices every second, and I need to resize/move the
form. At the momment I cant because of freezing.
I tried Thread thread = new Thread(new ThreadStart(tim er.start);
thread.IsBackgr ound = true;
thread.Start(); but that froze all together.
RegardS Robert

[Marc Gravell]

Re: timer/threading

OK; the timer (via SyncContext) fires on the UI thread. You then start
a thread, which immediately does a BeginInvoke back to the UI
thread...

At the moment you background thread is doing nothing useful; try to
split it so that it does something like:

private void liveprices()
{ // expecting this on a non-UI thread!
//TODO: go get the data into a new DataTable, array or
whatever
BeginInvoke((Me thodInvoker) delegate {
//TODO: update the grid
});
}

Now the "fetch" happends on the worker thread, and the UI update
happens on the UI thread.

However, every second seems optimistic for DataTable; I'm hoping
you're using a "get changes since <x>" mechanism in the database?

And note that if your datatable is UI bound you can only touch it from
the UI thread.

Marc

[RobcPettit@yahoo.co.uk]

Re: timer/threading

Thanks for your reply, thats improved peformance. I dont get complete
freeze. I still get it for a split second and im guessing this is
because the updates on the ui thread. My grids not linked to a
database, Im fetching data from the internet and updating the grid.
Ive no need to retain the data in a database.
Regards Robert

[RobcPettit@yahoo.co.uk]

Re: timer/threading

Thanks Nicholas, Threading is complicated. Ok, Am I runderstanding
this correctly then, what I was doing was calling my thread to do all
the work, on the UI thread. When infact I should have done my work
first, then called the thread to update the UI. In which case does
this meen in general, when you preform tasks such as
calculations,fe tching etc these are on seperate thread to the UI
until such time you invoke thread. Sorry I hope that makes sense.
Regards Robert

[RobcPettit@yahoo.co.uk]

Re: timer/threading

Thanks for taking the time to explain. Ive been doing it the wrong way
round, which explains why ive had problems with other programs. Still
its fun. Thanks again.
Regards Robert

[RobcPettit@yahoo.co.uk]

Re: timer/threading

Thanks for your replys, Im reading about system.threadin g.timer along
with threading period. Its takes some getting into.
Regards Robert