Programming Forums > Application Development > C#

hbe02 · Mar 26th, 2008, 6:25 PM

hi all,
it is to my knowledge that the timer component or class is used like some kind of count down timer that triggers an event. Now how can i instead trigger an event(function) at a certain time or date. like calender event. on 22/12/2009 at 11:00 am.
can this be done in an even triggered environment.. cause i can think of a very inefficient way of polling at every 5 minutes or so... but that is very wastefull!

Freaky Chris · Mar 26th, 2008, 7:09 PM

just retrive the system clock time and the check to see if it equal to the time you are after... surely that would work no.

Somehting like this

 C# Syntax (Toggle Plain Text) 
 DateTime theDate = DateTime.Parse("27 Mar 2008 00:26:00");
if (DateTime.Now => theDate)
{
     MessageBox.Show((DateTime.Now).ToString());
}
 DateTime theDate = DateTime.Parse("27 Mar 2008 00:26:00");
if (DateTime.Now => theDate)
{
     MessageBox.Show((DateTime.Now).ToString());
}

hbe02 · Mar 28th, 2008, 5:46 PM

yes that would definitely work. but you would have to poll that if statement on every second. isnt that kind of unpractical? isnt there some kind of event based approach?

Freaky Chris · Mar 28th, 2008, 5:59 PM

if you were to use a timer you could acheive this perhaps,

so if you were to start a timer when the app loads, it checks the date that it should preform some function at. Compares it to the current date to check to see if it should run the function.
if not it callsback to itself and check again etc.

C# isn't really the area i code in so supply sample code is an issue but something like that should work...if not i'll re-think again

Jabo · Mar 28th, 2008, 7:39 PM

In VB, and C# I'm sure, you can adjust the DateTime to just show the date and evaluate the date. So you don't have to poll every second, you could poll twice a day, and if it finds the date it's looking for, BOOM goes the dynamite.

OpenLoop · Mar 29th, 2008, 8:30 AM

Create a timer in your class:

c# Syntax (Toggle Plain Text)

public partial class Form1 : Form
    {...
        Timer timer;

Initialize the timer in the class constructor:

 c# Syntax (Toggle Plain Text) 
public Form1()
        {
            InitializeComponent();
...
            timer = new Timer();
            timer.Interval = 100;         //calls the fuction specified below every 100ms (1/10 sec)
            timer.Tick += new EventHandler(CheckTime);   //specify function to call every tick
            timer.Start();                    //start the timer
...
public Form1()
        {
            InitializeComponent();
...
            timer = new Timer();
            timer.Interval = 100;         //calls the fuction specified below every 100ms (1/10 sec)
            timer.Tick += new EventHandler(CheckTime);   //specify function to call every tick
            timer.Start();                    //start the timer
...

create the function to be called every tick and put Chris's code in it:

 c# Syntax (Toggle Plain Text) 
void CheckTime(object sender, EventArgs e)
{
    DateTime theDate = DateTime.Parse("27 Mar 2008 00:26:00");
    if (DateTime.Now => theDate)
    {
         MessageBox.Show((DateTime.Now).ToString());
         timer.Stop();               //if the event is no longer to be checked for, stop the timer
    }
}
void CheckTime(object sender, EventArgs e)
{
    DateTime theDate = DateTime.Parse("27 Mar 2008 00:26:00");
    if (DateTime.Now => theDate)
    {
         MessageBox.Show((DateTime.Now).ToString());
         timer.Stop();               //if the event is no longer to be checked for, stop the timer
    }
}

Ooble · Mar 29th, 2008, 10:19 PM

There isn't a way to have a function called at a specific time - the only way to do it is to poll the clock. Of course, if you were to poll it once every minute or less, the processor time dedicated to your task would be so negligible that no one would care.

Jimbo · Mar 29th, 2008, 11:58 PM

If you know the time you want it to fire at, you can sleep the thread for how long it takes to reach that time. Something along the lines of this pseudo-code:

(Toggle Plain Text)

DateTime target = "sometime";
Thread.Sleep(target - DateTime.Now);
// do your task

At work, we have a tool which basically runs on a timer every 15 seconds, checks an XML file to see if any of the tasks listed are due to run, and checks if any tasks have been added, then sleeps again. So, the polling is also a feasible design, give or take a few seconds.

Ooble · Mar 30th, 2008, 1:14 AM

And if the clock's wrong and the user changes it while you're sleeping?

Jimbo · Mar 30th, 2008, 1:51 AM

Quote:

Originally Posted by Ooble

And if the clock's wrong and the user changes it while you're sleeping?

That will be a problem with any polling solution, unless you assume that the first method I mentioned is put into action when the clock is set correctly

Mar 26th, 2008, 6:25 PM	#1
hbe02 Hobbyist Programmer Join Date: Mar 2006 Location: Lebanon Posts: 148 Rep Power: 3	scheduled events hi all, it is to my knowledge that the timer component or class is used like some kind of count down timer that triggers an event. Now how can i instead trigger an event(function) at a certain time or date. like calender event. on 22/12/2009 at 11:00 am. can this be done in an even triggered environment.. cause i can think of a very inefficient way of polling at every 5 minutes or so... but that is very wastefull!

Mar 26th, 2008, 7:09 PM	#2
Freaky Chris Hobbyist Programmer Join Date: Dec 2007 Location: England Posts: 169 Rep Power: 1	Re: scheduled events just retrive the system clock time and the check to see if it equal to the time you are after... surely that would work no. Somehting like this C# Syntax (Toggle Plain Text) DateTime theDate = DateTime.Parse("27 Mar 2008 00:26:00"); if (DateTime.Now => theDate) { MessageBox.Show((DateTime.Now).ToString()); } DateTime theDate = DateTime.Parse("27 Mar 2008 00:26:00"); if (DateTime.Now => theDate) { MessageBox.Show((DateTime.Now).ToString()); } Last edited by Freaky Chris; Mar 26th, 2008 at 7:29 PM.

Mar 28th, 2008, 5:46 PM	#3
hbe02 Hobbyist Programmer Join Date: Mar 2006 Location: Lebanon Posts: 148 Rep Power: 3	Re: scheduled events yes that would definitely work. but you would have to poll that if statement on every second. isnt that kind of unpractical? isnt there some kind of event based approach?

Mar 28th, 2008, 5:59 PM	#4
Freaky Chris Hobbyist Programmer Join Date: Dec 2007 Location: England Posts: 169 Rep Power: 1	Re: scheduled events if you were to use a timer you could acheive this perhaps, so if you were to start a timer when the app loads, it checks the date that it should preform some function at. Compares it to the current date to check to see if it should run the function. if not it callsback to itself and check again etc. C# isn't really the area i code in so supply sample code is an issue but something like that should work...if not i'll re-think again __________________ Who said i couldn't program `sarcasm = raw_input('Type in a sarcastic remark: ') print sarcasm`

Mar 28th, 2008, 7:39 PM	#5
Jabo Not a user? Join Date: Sep 2007 Posts: 245 Rep Power: 1	Re: scheduled events In VB, and C# I'm sure, you can adjust the DateTime to just show the date and evaluate the date. So you don't have to poll every second, you could poll twice a day, and if it finds the date it's looking for, BOOM goes the dynamite.

Mar 29th, 2008, 8:30 AM	#6
OpenLoop Expert Programmer Join Date: May 2005 Location: East Lansing, MI Posts: 663 Rep Power: 4	Re: scheduled events Create a timer in your class: c# Syntax (Toggle Plain Text) public partial class Form1 : Form {... Timer timer; public partial class Form1 : Form {... Timer timer; Initialize the timer in the class constructor: c# Syntax (Toggle Plain Text) public Form1() { InitializeComponent(); ... timer = new Timer(); timer.Interval = 100; //calls the fuction specified below every 100ms (1/10 sec) timer.Tick += new EventHandler(CheckTime); //specify function to call every tick timer.Start(); //start the timer ... public Form1() { InitializeComponent(); ... timer = new Timer(); timer.Interval = 100; //calls the fuction specified below every 100ms (1/10 sec) timer.Tick += new EventHandler(CheckTime); //specify function to call every tick timer.Start(); //start the timer ... create the function to be called every tick and put Chris's code in it: c# Syntax (Toggle Plain Text) void CheckTime(object sender, EventArgs e) { DateTime theDate = DateTime.Parse("27 Mar 2008 00:26:00"); if (DateTime.Now => theDate) { MessageBox.Show((DateTime.Now).ToString()); timer.Stop(); //if the event is no longer to be checked for, stop the timer } } void CheckTime(object sender, EventArgs e) { DateTime theDate = DateTime.Parse("27 Mar 2008 00:26:00"); if (DateTime.Now => theDate) { MessageBox.Show((DateTime.Now).ToString()); timer.Stop(); //if the event is no longer to be checked for, stop the timer } }

Mar 29th, 2008, 10:19 PM	#7
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	Re: scheduled events There isn't a way to have a function called at a specific time - the only way to do it is to poll the clock. Of course, if you were to poll it once every minute or less, the processor time dedicated to your task would be so negligible that no one would care. __________________ Me :: You :: Them

Mar 29th, 2008, 11:58 PM	#8
Jimbo Battle Programmer Join Date: Feb 2006 Location: Bellevue, WA, USA Posts: 748 Rep Power: 3	Re: scheduled events If you know the time you want it to fire at, you can sleep the thread for how long it takes to reach that time. Something along the lines of this pseudo-code: (Toggle Plain Text) DateTime target = "sometime"; Thread.Sleep(target - DateTime.Now); // do your task DateTime target = "sometime"; Thread.Sleep(target - DateTime.Now); // do your task At work, we have a tool which basically runs on a timer every 15 seconds, checks an XML file to see if any of the tasks listed are due to run, and checks if any tasks have been added, then sleeps again. So, the polling is also a feasible design, give or take a few seconds. __________________ <insert disclaimer here> <insert shameless plug for Visual Studio here>

Mar 30th, 2008, 1:14 AM	#9
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	Re: scheduled events And if the clock's wrong and the user changes it while you're sleeping? __________________ Me :: You :: Them

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Programming Forums > Application Development > C#

scheduled events