Events being sent to disabled control - c#

I have a problem that I'd like some advice on. I have a button in my GUI that starts a complicated setup sequence (to connect to a analogue to digital converter and start logging data from an echo sounder). Once it is finished setting up, the button changes from START to STOP and has the expected behaviour. What I was experiencing is that during the long operation, if the user clicked on the button again (even though it was disabled) the event would still be sent to the button once it was reenabled. The only way I've found to make this work properly is to call Application.DoEvents() before enabling the button again. All I really want to do is swallow up the events destined for my button, so DoEvents() seems a bit heavy handed. Since people seem to be unanimously against calling DoEvents() I'm hoping that the bright minds here can help me come up with an alternative solution. Note I haven't tried my demo code but it follows my real code closely, excepting the really long methods.
Is there an alternative way to accomplish this?
Is it safe(ish) to call DoEvents() from the completion portion of the background worker?
public class Form1 : Form
{
BackgroundWorker worker;
Button startButton;
bool state;
public Form1() {
state = false;
BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += new DoWorkEventHandler(StartSequence);
worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(ToggleButton);
startButton = new Button();
startButton.Text = "START";
startButton.Click += new System.EventHandler(StartClicked);
this.Controls.Add(startButton);
}
private void StartClicked( object sender, EventArgs e ) {
startButton.Enabled = false;
worker.RunWorkerAsync( !state );
}
private void StartSequence( object sender, DoWorkEventArgs e ) {
bool onState = (bool) e.Argument;
if ( onState ) {
RunReallyLongStartupSequence();
}
else {
RunReallyLongStopSequence();
}
state = onState;
}
private void ToggleButton( object sender, RunWorkerCompletedEventArgs e ) {
startButton.Text = state ? "STOP" : "START";
// THIS IS WHAT I AM WORRIED ABOUT!
Application.DoEvents();
startButton.Enabled = true;
}
}

Application.DoEvents() isn't heavy-handed, and I don't think programmers are unanimously opposed to DoEvents in all cases. DoEvents has a bad reputation because it has traditionally been used as a magical hack fix for badly-written code. In your case, it is the proper and normal way to deal with your situation.
In Windows, the situation you describe (where clicks on disabled buttons are applied when the buttons are re-enabled) is actually normal, expected behavior for a control. However, this does not mean that it is always desirable behavior from a programmer's standpoint, and if you have users that are prone to clicking away on disabled buttons, then the simplest way is to use DoEvents, which is nothing more than a method telling the form to go ahead and process any events it has queued up. Use it proudly!

First of all, I do not find DoEvents() bad at all, especially when it comes to gui, you can't imagine how many times it has helped me , and if you create things like progress bars, it is pretty much mandatory if you want to see it update, all I'm saying is that I don't really get why it is considered a bad command.
On the topic though, what I usually do in such situations is not disable the control at all
I use something similar to the following
public Class myForm :Form
{
private bool _working = false;
public myForm()
{
_working = true;
//code here
this.btnDoStuff.Click += new System.EventHandler(DoStuffClick);
_working = false;
}
private void DoStuffClick(object sender, EventArgs e)
{
if (_working) return;
_working = true;
DoStuff();
_working = false;
}
private void DoStuff()
{
//your code goes here
}
}
I find that the above helps me when it comes to allowing the user to do only one thing at a time, and if I want to be able to allow the user to do multiple stuff( for example while the command executes , to be able to press other buttons) I usually put the DoStuff() code to execute in a different thread
In case you were wandering, the reason I use an extra method (DoStuff()) to perform the actions, is that sometimes I need to execute code form other methods in one method, and if the _working flag is set to true, I can't call DoStuffClick(null , new EventArgs()) as it will not do anything
I hope I helped
p.s. yes I know it's been two years, but I only joined stackoverflow the other day (:

Related

Avoid UI buttons to run function twice after fast click

How do I avoid my UI buttons to run functions twice if clicked (accidentally) twice or more in a short time?
I have a UI button that calls a StartGame function in my game script. I attached the script to the button in the inspector. The function sets a few variables in order for the game to start.
If I accidentally click the button twice really quickly, the start function is executed twice and thus it screws up my variables. How do I avoid that?
I am thinking of splitting up the function so that it checks if it's already started, but that seems like a bit complex. Isn't there a standard setting in Unity UI or some standard code I missed? Tried to google but not much luck.
Simplified example of my code:
public void StartGame() {
MenuAnimator.SetBool ("Startbutton", false); // animates my start game panel off the screen.
lives = lives - 1;
Do Rest of Code();
}
In this case, clicking the UI menu Start Game button multiple times causes two or more lives to be deducted.
There's no need for a lock, just have a boolean that flips each click and the button only triggers a response when the bool is true.
first click -> true -> response.
second click -> false -> return.
What about something like this? This will prevent double clicks that happen within 1 second (or however many you want)
bool buttonLocked;
System.Timers.Timer t = new System.Timers.Timer(1000); //however many milliseconds
t.Elapsed += new EventHandler(resetFlag);
private void button_clicked(object sender, EventArgs e){
if(!buttonLocked){
// Handle Click
buttonLocked= true;
t.Enabled = true;
}
}
private void resetFlag(){
buttonLocked = false;
t.Enabled = false;
}
Or you could probably just use whether or not the timer is enabled as a flag assuming the timer is properly initialized. I like having a separate flag though for readability.
Full disclosure- I'm at a bar typing this on my phone so it's untested but I think that should work
Due the fact that I canno't comment, here is my answer.
You can lock the variable.
First create a lock
private readonly object _locker = new object();
In your lock property set/get
get { lock (_locker) { return this.myVar; } }
set { lock (_locker) { this.myVar = value; } }
Now you can lock this MyVar variable using
public void MethodA()
{
lock(_locker)
{
if(myVar == 1)
myVar = 0;
}
}
This is mostly used with multi-threading but It should do the job for you.

Why is UI unresponsive while being programmatically controlled?

I hand-rolled a MVC-style implementation of a game that I want to autoplay. By "autoplay" I mean that the buttons that normally a user would click while playing I want a controller to automatically initiate. That way I can watch the game play itself for quality control reasons. This particular game has a lot of code, so instead of providing it as an example I've created a silly HelloWorld example using the same approach.
Before I provide the example, here is my issue: everything you see below is functional, and "works"; except for one thing: I'm unable to shut-off the autoplay because the UI becomes unresponsive and the button to turn it off won't respond to a click event.
First create a .Net 4.6.1 winforms project in a solution. (.net version probably doesn't matter as long as it is >= 4.5). Create a Form that looks like this:
In the code behind, copy paste this: (change names as needed to compile)
using System;
using System.Threading;
using System.Windows.Forms;
namespace WinformsExample
{
public partial class HelloWorldView : Form
{
private readonly HelloWorldController MyHelloWorldController;
public HelloWorldView()
{
InitializeComponent();
MyHelloWorldController = new HelloWorldController();
}
private void button1_Click(object sender, EventArgs e)
{
MyHelloWorldController.HelloWorldRequested();
if (MyHelloWorldController.IsAutomated)
{
Thread.Sleep(2000);
button1.PerformClick();
}
}
private void HelloWorldView_Load(object sender, EventArgs e)
{
MyHelloWorldController.HelloWorldRequestedEvent += OnHelloWorldRequested;
}
private void OnHelloWorldRequested(HelloWorldParameters parameters)
{
textBox1.Text += parameters.HelloWorldString + Environment.NewLine;
textBox1.Update();
}
private void button2_Click(object sender, EventArgs e)
{
MyHelloWorldController.IsAutomated = !MyHelloWorldController.IsAutomated;
if (MyHelloWorldController.IsAutomated)
{
button2.Text = "hello world - is on";
button2.Update();
button1.PerformClick();
}
else
{
button2.Text = "hello world - is off";
button2.Update();
}
}
}
}
And create a class titled HelloWorldController.cs and copy paste this in to it:
namespace WinformsExample
{
public class HelloWorldParameters
{
public string HelloWorldString { get; set; }
}
public delegate void HelloWorldEventHandler(HelloWorldParameters parameters);
public class HelloWorldController
{
private readonly HelloWorldParameters _parameters;
public event HelloWorldEventHandler HelloWorldRequestedEvent;
public bool IsAutomated { get; set; }
public HelloWorldController()
{
_parameters = new HelloWorldParameters();
}
public void HelloWorldRequested()
{
_parameters.HelloWorldString = "Hello world!!";
if (HelloWorldRequestedEvent != null)
HelloWorldRequestedEvent(_parameters);
}
}
}
...go ahead and rename things if you need to. Now build the program. Click the first button. You will see "hello world". Now click the second button, you will see "hello world" printed every 2 seconds.
The way I thought this would work is that by clicking button2 a second time, that it would stop the autoplay. However, the UI is unresponsive and the button click event never happens.
What is going on here that is causing the UI to be unresponsive and how can I fix it so that I get the intended behavior?
*UPDATE - HERE IS THE SOLUTION *
Keep everything the same as above except for HelloWorldView.cs. Remove the call to Thread.Sleep(). Drag and drop a timer from the toolbox to the design surface. You will see an icon on the bottom of the designer surface labeled
timer1
Copy paste the following code in to HelloWorldView.cs. Compile and execute. If everything is correct you should be able to turn on and off the "hello world" display by clicking the button at any time - the UI stays responsive.
using System;
using System.Windows.Forms;
namespace WinformsExample
{
public partial class HelloWorldView : Form
{
private readonly HelloWorldController MyHelloWorldController;
public HelloWorldView()
{
InitializeComponent();
MyHelloWorldController = new HelloWorldController();
}
private void onTimerTick(object sender, EventArgs e)
{
button1.PerformClick();
}
private void OnHelloWorldRequested(HelloWorldParameters parameters)
{
textBox1.Text += parameters.HelloWorldString + Environment.NewLine;
textBox1.Update();
}
private void HelloWorldView_Load(object sender, EventArgs e)
{
MyHelloWorldController.HelloWorldRequestedEvent += OnHelloWorldRequested;
}
private void button1_Click(object sender, EventArgs e)
{
MyHelloWorldController.HelloWorldRequested();
}
private void button2_Click(object sender, EventArgs e)
{
MyHelloWorldController.IsAutomated = !MyHelloWorldController.IsAutomated;
if (MyHelloWorldController.IsAutomated)
{
button2.Text = "hello world - is on";
button2.Update();
timer1.Interval = 2000;
timer1.Tick += onTimerTick;
timer1.Start();
}
else
{
timer1.Stop();
button2.Text = "hello world - is off";
button2.Update();
}
}
}
}
WinForms uses a single message pump thread (called the UI thread). (If you are unfamiliar with the concept you should research Windows messages and Windows message pump).
Thread.Sleep causes the currently executing thread the sleep, or pause, for a time. This sleep/pause is like death to the thread - it is aware of nothing and unable to do anything.
As the currently executing thread in a WinForms app is usually the UI thread - Thread.Sleep will cause the UI to become unresponsive because it is no longer able to pump messages.
An alternative design would be to use a form-based Timer. Place your game playing code in the Timer's Tick event.
What is going on here that is causing the UI to be unresponsive and how can I fix it so that I get the intended behavior?
There are essentially two reasons why your app becomes unresponsive.
1. Thread.Sleep() in UI thread
GUI applications on Windows are generally driven by messages (mouse clicks; keyboard; screen drawing) posted to it which are placed on a queue. The UI thread processes these messages one by one dispatching the message to the appropriate handler. In this way it is known as the Message Pump. If during processing one of these messages too much time elapses, then the UI will appear to freeze. Event handlers should be as fast as possible.
During your click handlers you are using Thread.Sleep(2000); which will prevent the UI thread from updating the UI of your application, in essence simulating an event handler that takes far too long to process an event. It is perhaps no different to say performing a lengthy database or WCF operation on the UI thread, hence why people tend to put such calls on a separate thread or task.
Recommend you remove the Thread.Sleep and replace it with a timer as others have indicated.
2. Infinite Recursive Loop on button1 handler
When you click button2 for the first time, the click handler for button2 is invoked where automation is enabled. You then simulate button1 being clicked via button1.PerformClick();.
During the call to button1.PerformClick, the click handler for button1 button1_Click() is invoked. It is there that you sleep for 2 seconds (which isn't healthy for the UI) but the secondary problem is that you immediately call button1.PerformClick(); from inside the button1 click handler, in essence setting up an infinite recursive loop.
If you were to remove the Thread.Sleep(2000) your app will eventually lead to a StackOverflowException. Your code as it stands now (even with the sleep) will still overflow, it's just that it will take much longer to become apparent.
Again, consider replacing it with a timer.
3. Exclusivity
It's important to note that ignoring the stack fault for a moment, the design is such that your app can't do anything else whilst this infinite loop is running. So if your game had other buttons to click; scores to display; sound effects to play; all from the point of view of the button2 handler, most likely it will never happen because it is too busy exclusively processing button1.
Conclusion
Keep UI responsive: Avoid Thread.Sleep() in your code
Avoid recursion: Don't use PerformClick() for a button whilst you are inside the click handler for said button
Your "Thread.Sleep()" call puts the UI thread to sleep. Use a Timer instead. Then terminate the Timer on the second press. (You could also do this with Tasks, if you want to use another thread you need to make the 2 threads communicate in someway so that the UI thread is the only one actually updating the UI)
Desktop applications have a so called UI thread. It's basically an infinite loop which keeps checking if something happened, such as a mouse click, and redraws the window if needed. Coding in WinAPI you would need to write this loop yourself, WinForms and other UI frameworks hide it away. But your click handler is called from inside this loop. So if your code takes too much time - like, because you call Thread.Sleep inside - the loop will not continue and will not be able to process anything that is happening to the application. This why long-running processes need to take place on a separate thread.
As others have said, you are blocking the UI thread with the Thread.Sleep and recursive button1.PerformClick(); call. You have to let the UI run as freely as possible and let it go idle quickly.
So, just for the fun of it I have rewritten your code to do just that. I've also implemented it with Microsoft's Reactive Extensions (Rx) - just NuGet "Rx-WinForms" to get the bits. Rx allows you to do some very funky things that you can't easily do with events.
Here's your form now:
public partial class HelloWorldView : Form
{
private readonly HelloWorldController MyHelloWorldController =
new HelloWorldController("Hello world!!", TimeSpan.FromSeconds(1.0));
public HelloWorldView()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
MyHelloWorldController.Messages
.ObserveOn(this)
.Subscribe(message =>
{
textBox1.Text += message + Environment.NewLine;
});
MyHelloWorldController.IsAutomateds
.ObserveOn(this)
.Subscribe(isAutomated =>
{
button2.Text = "hello world - is " + (isAutomated ? "on" : "off");
});
}
private void button1_Click(object sender, EventArgs e)
{
MyHelloWorldController.Trigger();
}
private void button2_Click(object sender, EventArgs e)
{
MyHelloWorldController.IsAutomated = !MyHelloWorldController.IsAutomated;
}
}
You'll notice that I've simplified down the UI. It really does as little as possible to update itself and to notify the HelloWorldController of its actions.
The worst part of the code are the two .Subscribe calls in Form1_Load. These are simply looking at the two observables (Rx's version of events if you like) and makes sure the events are run on the UI thread with the .ObserveOn(this) call, and then they subscribe to values produced from the HelloWorldController.
The UI is simply updating itself from the controller and telling the controller what it is doing. There is virtually no logic being performed in the UI. This is how it should be with any MVC-style coding.
Now the HelloWorldController is where the fun is.
It starts off pretty simply:
private string _message;
private TimeSpan _automatedPeriod;
public HelloWorldController(string Message, TimeSpan automatedPeriod)
{
_message = Message;
_automatedPeriod = automatedPeriod;
}
This is basically the information about what message to send to the UI and how often when the controller is automating the values.
It then tracks whether it is automated or not:
private bool _isAutomated = false;
Now it contains the Rx observables - these are like the events you were using.
private Subject<string> _messages = new Subject<string>();
public IObservable<string> Messages { get { return _messages.AsObservable(); } }
private Subject<bool> _isAutomateds = new Subject<bool>();
public IObservable<bool> IsAutomateds { get { return _isAutomateds.AsObservable(); } }
private SerialDisposable _serialSubscription = new SerialDisposable();
In Rx an IObservable<T> is something I can subscribe to to get a series of values - just like an event. The Subject<T> is something that I can manually push values into, but it also can be an IObservable<T> that can be subscribed to. It's the pair of these that lets me raise events. Think of the Subject<string> to be the equivalent of the HelloWorldRequested method in your code and the IObservable<string> to be the equivalent of the HelloWorldRequestedEvent event.
If I call _messages.OnNext("Hello") then any subscribers to IObservable<string> Messages would get a "Hello" sent to them. Just like an event.
IsAutomated looks like this:
public bool IsAutomated
{
get { return _isAutomated; }
set
{
_isAutomated = value;
_isAutomateds.OnNext(value);
if (_isAutomated)
{
this.Trigger();
}
}
}
So it does its job of updating its own internal state, but it also calls _isAutomateds.OnNext(value) to push out the updates to any subscribers of IObservable<bool> IsAutomateds. It also works out if it needs to trigger the controller to produce messages with the this.Trigger() call.
Finally the Trigger method looks like this:
public void Trigger()
{
if (_isAutomated)
{
_serialSubscription.Disposable =
Observable
.Interval(_automatedPeriod)
.StartWith(0)
.TakeUntil(_isAutomateds.Where(x => x == false))
.Subscribe(n => _messages.OnNext(_message));
}
else
{
_messages.OnNext(_message);
}
}
The easy part of this is when the _isAutomated is false then it simply sends one message out via the _messages.OnNext(_message) call.
When _isAutomated is true it uses some of the coolness of Rx to set up effectively a timer to produce values every TimeSpan _automatedPeriod. From your code you wanted every 2 seconds so the TimeSpan would be TimeSpan.FromSeconds(2.0).
Observable.Interval(_automatedPeriod) defines a timer that begins producing values after the first period of time and then every period of time between.
So the .StartWith(0) says that it should immediately produce a value when it is subscribed to.
The .TakeUntil(_isAutomateds.Where(x => x == false)) is the best part here - it says that it will take the values from the the Observable.Interval(_automatedPeriod).StartWith(0) and stop when it gets a value from _isAutomateds.Where(x => x == false) - in other words when the IsAutomated is set to false.
The .Subscribe(n => _messages.OnNext(_message)); simply pushes a value to the _messages subject so that all subscribers of IObservable<string> Messages gets their messages.
Just put all of the HelloWorldController I've given you in public class HelloWorldController { ... } and you're good to go.
The works I think like it should and shows how lightweight the UI code can be.
I hope you find this worth playing with.
You'll need to add these using's to the top of your code to get all of the code to compile:
using System.Reactive.Disposables;
using System.Reactive.Linq;
using System.Reactive.Subjects;

C# Invoke button control on separate thread

I have seen a lot of questions about how to edit controls on c# form from a different thread but none make much sense to me. I understand that you can not change any UI from another thread than it's main. To make this work you have to use invoke and from there safely edit the control?
I have a button that starts writing in a file and the moment you press the button the button itself gets disabled so you can not start multiple threads that do exactly the same. When the writing is done I want the button to be available again but I can not get it working on this other thread.
I have this as the Generate_Click event from the form.
private void Generate_Click(object sender, EventArgs e)
{
Generate.Enabled = false;
int x = 512;
int y = 512;
MBrot mbrot = new MBrot(x, y);
PB_Update lb = new PB_Update(0, y, Generator_PB, Generate, mbrot, this);
lb.Start();
}
And this is in PB_Update.cs the ThreadWork() function, when the while loop is done the writing to the file is done and so is the thread so its ended and given a messagebox with "finished" now as last the button needs to be enabled again.
public void ThreadWork()
{
while (true)
{
if (currValue_ >= maxValue_)
break;
ThreadTick();
}
mb_.StopBrot();
t_.Interrupt();
MessageBox.Show("Finished!");
Generate_.Enabled = true;
}
For WinForms you can execute directly on the thread which the control was created on through the Control.BeginInvoke method, you can use Control.Invoke as well but, Control.BeginInvoke is preferred for UI operations.
public void ThreadWork()
{
while (true)
{
if (currValue_ >= maxValue_)
break;
ThreadTick();
}
mb_.StopBrot();
t_.Interrupt();
MessageBox.Show("Finished!");
Generate_.BeginInvoke((Action)delegate()
{
Generate_.Enabled = true;
});
}
Somehow, get a reference to the form that hosts the generate_ button (let's call it myform). Then, at the bottom of your ThreadWork:
myform.Invoke(new Action(() => {
myform.SetGenerateEnabled();
}));
And then inside your form create that method that enables the button appropriately. (I used a method rather than just updating the button directly so that you don't publicly expose the button.)
This executes the commands inside the { ... } on myform's thread, which is a UI thread, because it is UI. At least, that's what I understand. This is how I do all of my UI updating from other threads.
Here's a simple example of a way to kick off an async task that disables a button for 5 seconds and then enables it again. Meanwhile, the rest of the UI is functional.
Note that this async method exists in the same class as your Generate_Click event, and runs on the UI thread. This means that it can enable and disable the button. But the long running task executes on a separate thread, so it doesn't lock the UI.
Hopefully this sample provides you a base to modify for your own code:
private void Generate_Click(object sender, EventArgs e)
{
DisableButton(sender as Button, 5);
}
private async void DisableButton(Button sender, int secondsToDisable)
{
sender.Enabled = false;
// In your code, you would kick off your long-running process here as a task
await Task.Run(()=>Thread.Sleep(TimeSpan.FromSeconds(secondsToDisable)));
sender.Enabled = true;
}

How to use a BackgroundWorker to update multiple labels?

This is a follow up question to Updating a dialog from another form (The code and screenshots can be found there)
To solve my GUI hanging problem I received 2 recommendations:
Using Application.DoEvents()
Using a BackgroundWorker
The DoEvents() approach works, however it has been pointed out that I should not use it. Indeed, I notice that the GUI updates correctly but is unresponsive for short times.
That's why I want to use a BackgroundWorker and have read up on it.
I don't understand how I would implement it so that it can be used to update the 4 labels in my example code separately, though.
I want to show the progress (and update 4 dialog labels) as the program successfully finishes one job. The BackgroundWorker has only 1 DoWork() though. I have tried to use the e.Argument of the DoWorkEventArgs to differentiate between the different update methods but that attempt had failed.
public partial class BackgroundWorkerImportStatusDialog : Form
{
private BackgroundWorker dialogWorker = new BackgroundWorker();
private string path;
private string clientName;
public BackgroundWorkerImportStatusDialog()
{
InitializeComponent();
}
public void updateFileStatus(string path)
{
this.path = path;
dialogWorker = new BackgroundWorker();
dialogWorker.DoWork += new DoWorkEventHandler(updateLabels);
dialogWorker.RunWorkerAsync(UpdateComponent.FileStatus);
}
public void updatePrintStatus()
{
dialogWorker = new BackgroundWorker();
dialogWorker.DoWork += new DoWorkEventHandler(updateLabels);
dialogWorker.RunWorkerAsync(UpdateComponent.PrintStatus);
}
public void updateImportStatus(string clientName)
{
this.clientName = clientName;
dialogWorker = new BackgroundWorker();
dialogWorker.DoWork += new DoWorkEventHandler(updateLabels);
dialogWorker.RunWorkerAsync(UpdateComponent.ImportStatus);
}
public void updateArchiveStatus()
{
dialogWorker = new BackgroundWorker();
dialogWorker.DoWork += new DoWorkEventHandler(updateLabels);
dialogWorker.RunWorkerAsync(UpdateComponent.ArchiveStatus);
}
private void updateLabels(object sender, DoWorkEventArgs e)
{
MessageBox.Show(e.Argument.ToString());
if ((UpdateComponent) e.Argument == UpdateComponent.FileStatus)
{
t_filename.Text = path;
}
if ((UpdateComponent) e.Argument == UpdateComponent.PrintStatus)
{
t_printed.Text = "sent to printer";
}
if ((UpdateComponent) e.Argument == UpdateComponent.ImportStatus)
{
t_client.Text = clientName;
}
if ((UpdateComponent) e.Argument == UpdateComponent.ArchiveStatus)
{
t_archived.Text = "archived";
}
}
public enum UpdateComponent { FileStatus, PrintStatus, ImportStatus, ArchiveStatus}
And I can't imagine having 4 BackgroundWorkers for this pretty trivial dialog is the solution.
As I understand your question, you want to have your dialog form inform the user about 4 different aspects of your application running:
printing status
file status
import status
archiver status
Background worker could be used to periodically check each one. You may advanced progressbar by 25% after status of each operation is checked (and update your UI with appropriate information).
You may also try async programming - i.e. just start the operation, and lets your application continue. When the operation completes, your application will be notified, and could update information on the form.
Depending on the .NET framework you're using you may use async and await (avaialble since .NET 4.5 / C# 5 - async & await on MSDN) or classic approach to asynchronous programming.
Edit:
I am not sure that BackgroundWorker is the best solution in this situation. I can imagine having something like:
BackhgroundWorker checking things just once - i.e. check printing status once, file status once, import status once, archiver status once. This may sound silly, but it could be user behavior driver - i.e. explicitly launched when user clicks or invokes this mechanism any other way. ProgressBar could be put on the application's statausbar, so that user knows that 'application is actually doing something'.
Previous approach could be improved a bit - you never actually finish your job in BackgroundWorker - instead inside your main method you just have an infinite loop. This will allow you to check things periodically. In this approach there is no point in increasing the progress.
Sample for the second approach:
private void bg_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = sender as BackgroundWorker;
for (int i = 1; i <= 10; i++)
{
if (worker.CancellationPending == true)
{
e.Cancel = true;
break;
}
else
{
CheckPrintingStatus();
CheckFileStatus();
CheckImportStatus();
CheckArchiverStatus();
System.Threading.Thread.Sleep(5000); // sleep for 5 seconds
}
}
}
There is a question if this solution (second approach) is better than having a thread created explicitly. You could think of creating 4 different threads, so that each could check something else. This would be a bit heavier on the OS, but on the other hand you can set different sleep times for every operation.
If you go for bare threads - you may want to use ThreadPool instead of creating threads explicitly.

Stop loop in class from another class

So I have two event handlers button1_Click() and button2_Click()
In button1_Click() I have something running like this:
toGet = textbox1.Text;
got = 0;
while (got <= toGet)
{
//DoStuff
}
But button2_Click is supposed to be a stop button, and stop button1 early.
How do I go about this?
Thanks for the help. I saw this article here about it, but couldn't get it to work.
Windows.Forms answer
The least sophisticated method is this:
private bool m_stop;
private void button1_Click (object s, EventArgs ea)
{
try
{
// Don't forget to disable all controls except the ones you want a user to be able to click while your method executes.
toGet = textbox1.Text;
got = 0;
while (got <= toGet)
{
Application.DoEvents ();
// DoEvents lets other events fire. When they are done, resume.
if (m_stop)
break;
//DoStuff
}
finally
{
// Enable the controls you disabled before.
}
}
private void button2_Click (object s, EventArgs ea)
{
m_stop = true;
}
It has the distinct advantage of letting you execute button1_Click on the UI thread, still lets the UI respond to your stop button.
It has a disadvantage that you must protect against reentrancy. What happens if they click your button1 while button1_click is already executing!?!?
Edit: Another way I have used is to use a Timer instead of a loop. Then, the stop method just stops the timer.
As much as I understood, correct me if I'm wrong, you're on single thread.
Wired, but you can check for single boolean value inside the your While loop, just as post suggested.
May be to make life easier (may be this is what "couldn't get it to work" means) is inside loop call
1) Windows Forms: Application.DoEvents()
2) WPF (little bit more tricky) : DoEvents in WPF
This to make breathe system.
You need to start the process inside the button1 in new thread, and when you press the button2 flag a local variable to false to stop the loop. like:
using System.Threading;
private volatile bool _requestStop = false;
private readonly object _oneExecuteLocker = new object();
private void OnButton1Click(ojbect sender, EventArgs e)
{
new Thread(() =>
{
if (Monitor.TryEnter(_oneExecuteLocker))
{//if we are here that is means the code is not already running..
try
{
while (!_requestStop)
{
//DoStuff
}
}
finally
{
Monitor.Exit(_oneExecuteLocker);
}
}
}){ IsBackground = true }.Start();
}
private void OnButton2Click(object sender, EventArgs e)
{
_requestStop = true;
}
Notes:
When ever you want to update a UI control inside the newly created thread you should use contorl.Invoke(/*the code get/set or call method in the UI*/).
The Monitro.Enter is just to be sure that your code will not executed multiple time per click if it already running.

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