I just added some extra functionality to a Coding4Fun project. I have my project set up with an extra option to allow it to automatically change the background after X amount of time. X is set from a ComboBox. However, I know I've done this in a terrible way, as I have created a new timer class with System.Timers.Timer as a parent so when the static method in the ElapsedEventHandler is called, I'm able to get back to the form and call ChangeDesktopBackground().
What is a better way to call ChangeDesktopBackground() at a user defined interval?
Here is my current solution, which involves me casting the sender as my inherited timer, which then gets a reference to the form, which then calls the ChangeDesktopBackground method.
private static void timerEvent(object sender, System.Timers.ElapsedEventArgs e)
{
((newTimer)sender).getCycleSettingsForm().ChangeDesktopBackground();
}
Edit:Added coding sample to show current solution
I've written something like this before myself. System.Timers.Timer is overkill for this. You should probably use System.Windows.Forms.Timer, for a couple of reasons:
You're doing something that doesn't have to be too precise. The Windows timer is just a WM_TIMER message sent to your windows app's message pump, so you're not getting super great precision, but changing your wallpaper once a second is unrealistic. (I wrote mine to change every 6 hours or so)
When using a Windows Forms app that does some kind of timer-based task, you're going to run into all kinds of thread affinity issues if you go with System.Timers.Timer. Any Windows control has an affinity for the thread on which it was created, meaning that you can only modify the control on that thread. A Windows.Forms.Timer will do all that stuff for you. (For future nitpickers, changing wallpaper doesn't really count, cause it's a registry value change, but the rule holds generally)
Timers are probably the most straight-forward way of doing it, although I'm not sure you're using a timer correctly. Here's how I've used timers in my projects:
// here we declare the timer that this class will use.
private Timer timer;
//I've shown the timer creation inside the constructor of a main form,
//but it may be done elsewhere depending on your needs
public Main()
{
// other init stuff omitted
timer = new Timer();
timer.Interval = 10000; // 10 seconds between images
timer.Tick += timer_Tick; // attach the event handler (defined below)
}
void timer_Tick(object sender, EventArgs e)
{
// this is where you'd show your next image
}
Then, you'd connect your ComboBox onChange handler such that you'd be changing timer.Interval.
I would use Microsoft's Reactive Framework for this. Just NuGet "Rx-WinForms".
Here's the code:
var subscription =
Observable
.Interval(TimeSpan.FromMinutes(1.0))
.ObserveOn(this)
.Subscribe(n => this.getCycleSettingsForm().ChangeDesktopBackground());
To stop it just do subscription.Dispose().
Simple.
Related
I have multiple timers running on my windows app. Each timer_tick runs a code. Right now I am working on two processes.
private async void tmrProcessDelay_Tick
private async void tmrAutopay_Tick
Just recently added the tmrAutopay as an added process so that instead of sequential process, I made them work at the same time. The problem I am having is that I am not able to restart the process of the Autopay.
Timers are declared at the top as an instance when form loads.
private System.Windows.Forms.Timer tmrProcessDelay = new System.Windows.Forms.Timer();
private System.Windows.Forms.Timer tmrAutopay = new System.Windows.Forms.Timer();
tmrAutopay.Interval = 2000;
tmrAutopay.Enabled = false;
tmrAutopay.Tick += new EventHandler(tmrAutopay_Tick);
private async void tmrAutopay_Tick(object sender, EventArgs e)
{
messagebox("tick"); // correcting this one
txtNotes.AppendText("tick");
tmrAutopay.Enabled = false;
// do some code
tmrAutopay.Enabled = true;
}
EDIT: as per Michael Randall suggestion, I tried adding break point at the top. I got the issue. Just on the logic. I just thought that it doesn't start again because "tick" only appends once, so I assumed it only ran once. When I went adding the break point, it ticked again, but for some reason, it did not appendText, reason I did assume things. Going back to the problem, due to the existing logic, after
called tick one - appendtext
enabled = true - ticked but did not append
due to logic, it did not go to enabled = true again
The timer tick only runs after I enabled it the first time, then when its ticks, I set it to false to do some code then start it again after finishing.
I have yet to try this system timer solution, and also saw some post that timers won't run on background process, since I can run it one time, it means it can.. But I just wanna ask before I change timers if there are any reasons why I am having this issue?
if you want to make like background process then you can do window service application and implement more than one timer in that code. I had good working experience with this type of application and I am confident that it will work without any issue with multiple timers. the only thing you need to be careful in code is that in case if some code takes longer than expected and more than timer interval then it will start another thread which could end up as deadlock for that timer or crash the application. Each timer works independently and creates a new thread each time when it ticks.
I want to use a System.Windows.Forms.Timer to ensure that an event fires on the UI thread of an excel addin I'm creating. I construct the timer as follows:
private System.Windows.Forms.Timer _timer;
private void ThisAddIn_Startup(object sender, System.EventArgs e)
{
Debug.WriteLine("ThisAddIn_Startup:" + Thread.CurrentThread.ManagedThreadId);
_timer = new System.Windows.Forms.Timer();
_timer.Tick += new EventHandler(TimerEventHandler);
_timer.Interval = 500;
}
The timer is fired by a COM event from a library I am using:
private void OnEvent()
{
_timer.Start();
}
I then expect the _timer to call the following method when it ticks:
public void TimerEventHandler(object sender, EventArgs args)
{
_timer.Stop();
Debug.WriteLine("Tick: " + Thread.CurrentThread.ManagedThreadId);
}
As I understand, when I create the timer in the Addin thread, even though it is started from another thread (COM event in this case), it should fire on the thread that it was created on, i.e. the addin thread. However, this doesn't happen.
I have implemented this exact mechanism in an RTDServer I wrote in the past (as outlined by Kenny Kerr) and it works as expected but the _timer in this scenario never ticks.
I have also read other SO articles that point to the same behavior and can't figure out what is different about my addin setup?
EDIT:
The OnEvent() method is fired.
The winforms timer is a control and must be used by placing it on a form. You never add it to a control-collection, so I would not expect it to work properly. The documentation says the following
Implements a timer that raises an event at user-defined intervals. This timer is optimized for use in Windows Forms applications and must be used in a window.
Therefore, I would suggest that you use an instance of the System.Timers.Timer class. This class can be used anywhere.
Note that the Tick-event you use above, is called by another name in the System.Timer.Timer class, namely the Elapsed-event.
I initially meant to post this as comment, but it turned to be too long.
Firstly, your thread structure is a bit confusing to me, the way you described it. Put Debug.WriteLine("OnEvent:" + Thread.CurrentThread.ManagedThreadId) inside OnEvent and let us know all thread IDs you see from your debug output.
That said, the rules are:
You should create WinForms' Timer object on an STA thread, and the thread should be configured as STA before it starts.
This thread may or may not be the main UI thread (where your main form was created), but it still should execute a message loop (with Application.Run) for timer events to fire. There are other ways of pumping messages, but generally you do not control them from .NET code.
You should handle the events sourced by WinForms' Timer on the same thread it was created. You can then 'forward' these events to another thread context if you like (using SynchronizationContext Send or Post) but I can't think of any reasons for such complexity.
The answer by #Maarten actually suggests the right way of doing it, in my opinion.
I don't yet understand why the Forms.Timer doesn't operate as expected but the following excellent article explains in detail how to marshal work onto the UI thread: http://www.codeproject.com/Articles/31971/Understanding-SynchronizationContext-Part-I
How to schedule the event, for instance I need to call a method which should perform its action for every given seconds. I'm developing simple windows form app, I tried using like
while(true)
{
methodToBeScheduled();
Thread.Sleep(60000);
}
This particular piece of code makes my application "Not-responding" while its executing. I hope timer can do this or any other logic that you experts suggest, kindly please let me know.
Thanks!
You can use the WinForms timer:
Timer _timer;
// In constructor (or anywhere you want to start the timer, e.g. a button event):
_timer = new Timer();
_timer.Interval = 60000; // milliseconds
_timer.Tick += (sender, e) => methodToBeScheduled();
_timer.Start();
This will cause methodToBeScheduled to be called once every 60 seconds, roughly. It will be called on the main UI thread, so avoid doing any heavy processing in it.
The advantage of using this timer is that it's built-in, doesn't require thread synchronization, and is simple to use. The disadvantage is that the interval is not exact -- the actual interval will vary depending on what other messages need to be processed in the application, and is also at the mercy of the Windows system clock, which is only accurate to 10-20ms or so.
You can use a Timer(System.Threading.Timer).
using System;
using System.Threading;
Timer _timer = null;
_timer = new Timer(o =>
{
methodToBeScheduled();
});
_timer.Change(TimeSpan.Zero, TimeSpan.FromSeconds(60));
Var sequence = Observable.interval(1).publish
Sequence.subscribe ....
Will allow to subscribe to an observable that will fire an onnext every second. See reactive extension ..
Hate typing on iPads....
Yes, there are three different types of timers (all of which are named Timer but behave a little different) in .net. The windows.forms timer executes a function at a certain rate--it calls the function from the UI thread. The System.Threading Timer does the same but calls the function from another thread. There is another timer that I can't remember off the top of my head. You will have to pick one of them based on your circumstance.
Threading timer is my favorite. Here is an example if how to use it. Just keep in mind whatever you are calling is not done from the UI thread. May want to use the forms timer or synchronize things if that's an issue.
I'm really struggling with this. I'm creating a winforms application in visual studio and need a background timer that ticks once every half hour - the purpose of this is to pull down updates from a server.
I have tried a couple of different approaches but they have failed, either due to poor tutorial/examples, or to my own shortcomings in C#. I think it would be a waste of time to show you what I have tried so far as it seems what I tried was pretty far off the mark.
Does anyone know of a clear and simple way of implementing an asynchronous background timer that is easily understandable by a C# newbie?
// Create a 30 min timer
timer = new System.Timers.Timer(1800000);
// Hook up the Elapsed event for the timer.
timer.Elapsed += OnTimedEvent;
timer.Enabled = true;
...
private static void OnTimedEvent(object source, ElapsedEventArgs e)
{
// do stuff
}
with the usual caveats of: timer won't be hugely accurate and might need to GC.KeepAlive(timer)
See also: Why does a System.Timers.Timer survive GC but not System.Threading.Timer?
Declare member variable in your form:
System.Timers.Timer theTimer;
On form load (or whatever other time you need to start update polling), do:
theTimer = new System.Timers.Timer(1800000);
theTimer.Elapsed += PollUpdates;
theTimer.Start();
Declare your PollUpdates member function like this:
private void PollUpdates(object sender, EventArgs e)
{
}
I think you need to know about all timer classes. See Jon's answer below.
What kind of timer are you using?
System.Windows.Forms.Timer will execute in the UI thread
System.Timers.Timer executes in a thread-pool thread unless you
specify a SynchronizingObject
System.Threading.Timer executes its callback in a thread-pool thread
In all cases, the timer itself will be asynchronous - it won't "take up" a thread until it fires.
Source: Do .NET Timers Run Asynchronously?
I got a little problem with my application.
I would like to update something on my UI every 10 seconds. I first used a DispatcherTimer for this but it will block my UI for a short time because the update method needs to load something from the web and this operation needs some time.
Now I thought about some kind of background worker and I found BackgroundTasks.
The problem with Background tasks is, as far as I understood it correctly, that they are supposed to serve as updaters even if the app is suspended. I don't need that.
I only would like to update if my app is running not if it is suspended.
Is there a good way to solve this?
Any suggestions what to use for this?
Thanks in advance!
You need two things for it:
Timer
You can update the UI in System.Timers.Timer with the 10 seconds interval.
Dispatcher
You need to use Dispatcher.Invoke to change the UI without holding the main UI thread. Instead the method Process should be called on a separate thread (Timer method), other than main UI thread, and use Dispatcher in it to alert main UI thread for the change.
Process() // method to be called after regular interval in Timer
{
// lengthy process, i.e. data fetching and processing etc.
// here comes the UI update part
Dispatcher.Invoke((Action)delegate() { /* update UI */ });
}
You need to create a thread that runs the part of your code that gets and processes the information from the website. This way, your form will not hesitate because it will be on a different thread than the processing part.
This Article on code-project should get you started.
Also, you could start a timer, which has a elapsed event, that occurs every time the timer passes a certain time cycle.
http://www.dotnetperls.com/timer
The other answers are missing proper cleanup: When the timer fires in the exact moment that the window was closed, I would get an uncaught TaskCanceledException when trying to run Dispatcher.Invoke. I didn't find help for this problem in other questions. I was able to solve it by unregistering the timer callback when closing the window.
public partial class MainWindow : Window
{
Timer clockTimer = null;
public MainWindow()
{
clockTimer = new Timer(1.0); // 1 ms update to test for TaskCanceledException
clockTimer.Elapsed += Timer_Elapsed;
clockTimer.AutoReset = true;
clockTimer.Start();
Closed += (object sender, EventArgs e) => { clockTimer.Elapsed -= Timer_Elapsed; };
}
private void Timer_Elapsed(object sender, ElapsedEventArgs e) {
var now = DateTime.Now;
Dispatcher.Invoke((Action)delegate () {
UpdateTime(now);
});
}
}
Obviously this is not a good idea if the window was re-shown. I tried adding a dtor, but it would never get called, probably due to cyclic dependencies.
Disclaimer: I don't know C#, so this might not be the best or proper way of doing things.