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C# Form Application - Stop an ongoing process with a click of another button

Is it possible to stop an ongoing process with a button click in Windows form application?
For example, let's say there are 2 buttons, "START" and "STOP"
When you press "START", it will start an infinite loop, printing numbers from 1 to infinity.
When I press "STOP", the process should stop at that moment.
But the problem is, I cannot press the "STOP" button as it does not allow me, since there's an ongoing process.
Is there a way to overcome this?
I know there's something called "MethodInvoker", but I have no idea how that works or whether it is relevant to this.
private bool keepRunning = true;
public Form1()
{
InitializeComponent();
}
private void StartBtn_Click(object sender, EventArgs e)
{
var number = 1;
while (keepRunning)
{
Thread.Sleep(1000);
MesgeLabel.Text = "" + number++;
}
}
private void StopBtn_Click(object sender, EventArgs e)
{
//Cannot even click this button
keepRunning = false;
//or
Application.Exit();
}

EDIT 1:
If you need to interact with UI controls, doing it from a background task would throw invalid operation -> illegal cross thread exception. To overcome this,
check Control.InvokeRequired
if(myLabel.InvokeRequired)
myLabel.Invoke(new Action(() => myLabel.Text = newText));
else
myLabel.Text = newText;
You can start a Task by providing a CancellationToken and cancel the operation when the stop button is clicked.
The task will execute the infinite loop on another thread and your main thread (the UI thread) should not be affected and should be accessible.
Try this:
/*
Please add these on top of your form class
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
*/
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
CancellationTokenSource cancellationTokenSource;
CancellationToken cancellationToken;
private void CountToInfinity()
{
while (true)
{
cancellationToken.ThrowIfCancellationRequested();
Debug.WriteLine(new Random().Next());
}
}
private async void button1_Click(object sender, EventArgs e)
{
if (cancellationTokenSource == null)
{
cancellationTokenSource = new CancellationTokenSource();
cancellationToken = cancellationTokenSource.Token;
Task.Run((Action)CountToInfinity, cancellationToken);
}
}
private void button2_Click(object sender, EventArgs e)
{
if (cancellationTokenSource != null)
{
cancellationTokenSource.Cancel();
cancellationTokenSource.Dispose();
cancellationTokenSource = null;
}
}
}

If you have spawned a new process then you can call kill method.
Process myProcess = Process.Start("Notepad.exe")//starts new process
myProcess.Kill();// kills the process. save reference to myProcess and call kill on STOP button click
If you have started new thread then call abort method to stop the thread.
Thread thread = new Thread(new ThreadStart(method));
thread.Start();
thread.Abort(); // terminates the thread. call abort on STOP button click

When you press the "start" button, the code that runs and prints the numbers will run on the ui thread. (from your explanation, i assume that all you have is the message handler for the button press event and nothing else. e.g.: Not setting up a seperate thread.).
Running an infinite loop on the ui thread means, that you do not get any more time for processing other messages. (the thread that is responsible for processing the ui messages is stuck in your infinite loop.)
So, in order to be able to press the "stop" button, you need to run the code with the infinite loop in a different thread or in a different process altogether. This is what Arjun is trying to tell you. (if you want the code in the infinite loop to access resources from your form app, you need a thread. [the thread is inside the forms app process.])
please note: if you create a thread and run your number printing code inside that thread, this will not be the ui thread. Thus, you will not be able to interact with the forms controls as if you'd be on the ui thread. (i.e.: trying to set the windows.text in order to display your numbers will most likely throw an exception.)

Popup status window during a datagrid iteration update

I've spent 4 hours on this and totally failed.
I know that i need to use BackgroundWorker but all the tutorials refer to running a progress script on the actual form you are running the worker on.
I have a large datagrid, which the user can use a check box to "select all" and then press "UPDATE ALL"
This updates every grid with a bunch of options they choose.
For some users this may be 5 records which is nothing, but some might update 200 records with 5 options which takes about... 10-15 secs to iterate through them.
I have tried so many variations of running BGworker which loads a FrmLoading.Showdialog
Or trying to have BGworker "do work" running the code and then the main thread having the FrmLoading.Show()
However nothing is working.
If i have the update code in the background worker, it fails because the datagrid and everything is in a different thread.
The other way round, and it just hangs on FrmLoading.Show()
Any advice would be great.
I just can't seem to get my head around how to get this working for what seems to be an easy idea!
Current Update Code:
foreach (DataGridViewRow rowx in dataGridpatients.Rows)
{
//MessageBox.Show(Convert.ToBoolean(rowx.Cells["clnselected"].Value).ToString());
if (Convert.ToBoolean(rowx.Cells["clnselected"].Value) == true)
{
//if cycle has a value.
if (cmbcycle.SelectedIndex != -1)
{
rowx.Cells["clncycletype"].Value = cycle;
rowx.Cells["clnpackscollect"].Value = packs;
}
//if location has a value
if (cmblocation.SelectedIndex != -1)
{
location = Convert.ToInt32(cmblocation.SelectedValue);
rowx.Cells["clnlocation1"].Value = location;
}
if (cmbsize.SelectedIndex != -1)
{
size = Convert.ToInt32(cmbsize.SelectedValue);
rowx.Cells["clnpacksize"].Value = size;
}
if (chkDelivery.Checked == true)
{
rowx.Cells["clnDelivery"].Value = true;
}
if (chkSignSheet.Checked == true)
{
rowx.Cells["clnSigningSheet"].Value = true;
}
}
countupdated++;
}
foreach (DataGridViewRow row in dataGridpatients.Rows)
{
row.Cells["clnselected"].Value = false;
row.DefaultCellStyle.BackColor = Color.White;
}
cmbsize.SelectedIndex = -1;
cmblocation.SelectedIndex = -1;
cmbcycle.SelectedIndex = -1;
chkDelivery.Checked = false;
chkSignSheet.Checked = false;
#countupdated++;
I also have #CountSelected.
What i want to do is run this code above but have a popup overlay (dialog) with my logo + "Updating X%"
Where X = countupdated/countselected * 100
I now know i need to use the background worker and invoke for the above, but literally have no idea regarding how to invoke the grid and go from there.
I understand i need to invoke the variables I'm using
(eg. cmbcycle.SelectedIndex)
I know iterating through 150 records and updating individual cells is probably wrong,
My other option is creating a datatable from "selected" cells on that datatable
then Running the update via SQL instead of iterating through a bound table.
Then after the SQL i can re-create the table which will now have the new cell values updated in it?
Would that be a more appropriate way to do it?
Max rows on this table would be 200. Average ~70 so we are never talking 500 or 1000
EDIT:
So the checked answer works to run the background worker and refer to the controls on the form.
The issue is that if i do this:
backgroundWorker1.RunWorkerAsync();
splashy.ShowDialog();
Then the splash screen pops up after the background worker ends
If i do this:
splashy.ShowDialog();
backgroundWorker1.RunWorkerAsync();
Then the popup semi-forms and hangs until the end of the background worker, at which time it closes
because of the RunWorkerCompleted event.
EDIT:
I have no updated the code in DoWork and used Invokes to refer to the controls.
This works and the code runs fine.
I now need a popup ot appear showing the progress through the updates.
splashy.InvokeBy(() =>
{
splashy.Show();
});
backgroundWorker1.RunWorkerAsync();
Does not work. It causes the popup but freeze
splashy.ShowDialog();
backgroundWorker1.RunWorkerAsync();
Allows the Dialog to show (not 'frozen' and distorted) However the Lab (lblprogress) does not update.
This is because the form never get to the RunWorker method, it is stuck at ShowDialog.

It would be a good idea to make modifications on your DataSource itself and then bind it with the DataGridView.
But as from your existing code if you want to access your controls/UI to update or change values from BackgroundWorker.RunWorkerAsync method or any other Thread call for that matter, you can create an extension method to .Invoke() the controls like:
public static class MyExtensions
{
public static void InvokeBy(this Control ctl, MethodInvoker method)
{
if (ctl.InvokeRequired)
ctl.Invoke(method);
else method();
}
}
Keep this static class under the same Namespace as your main class for convenience.
Thus this code:
foreach (DataGridViewRow rowx in dataGridpatients.Rows)
{
//your codes
}
Will become:
dataGridpatients.InvokeBy(() =>
{
foreach (DataGridViewRow rowx in dataGridpatients.Rows)
{
//your codes
}
});
Similarly,
if (cmbcycle.SelectedIndex != -1)
{
//your codes
}
Will become:
cmbcycle.InvokeBy(() =>
{
if (cmbcycle.SelectedIndex != -1)
{
//your codes
}
});
This way you van safely access your controls, while keeping your UI responsive at the same time. Update your Popup Status UI the same way!

This answer is based around o_O's answer.
The main issue is that i wanted the UI to actually update and the background worker to supply the splash.
Instead of running all the 'hard code' in the BGW, i left it in the original thread, but called a BGW to display a popup Dialog form.
so at the start of the "hard code" I used:
backgroundWorker1.RunWorkerAsync();
This called:
FrmSplash splashy;
private void backgroundWorker1_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
{
splashy = new FrmSplash();
splashy.ShowDialog();
}
In order to remove the dialog box, at the end of the code in the GUI thread, i used:
splashy.InvokeBy(() =>
{
splashy.Close();
}
);
backgroundWorker1.CancelAsync();
Which uses the extension supplied by O_o
public static class MyExtensions
{
public static void InvokeBy(this Control ctl, MethodInvoker method)
{
if (ctl.InvokeRequired)
ctl.Invoke(method);
else method();
}
}
I have also built a label update into splashy
So i could call
splashy.InvokeBy(() =>
{
splashy.SetStatus(countupdated.ToString());
}
);
As i iterated through the datagridview rows. This updated the label on the splash screen :)

C# BackgroundWorker

I have a button that on click event I get some information from the network.
When I get information I parse it and add items to ListBox. All is fine, but when I do a fast double-click on button, it seems that two background workers are running and after finishing all work, items in the list are dublicated.
I want to do so that if you click button and the proccess of getting information is in work, this thread is stopping and only after first work is completed the second one is beginning.
Yes, I know about AutoResetEvent, but when I used it it helped me only one time and never more. I can't implement this situation and hope that you will help me!
Now I even try to make easier but no success :( : I added a flag field(RefreshDialogs)(default false), when the user clicks on button, if flag is true(it means that work is doing), nothing is doing, but when flag field is set to false, all is fine and we start a new proccess.
When Backgroundwork completes, I change field flag to false(it means that user can run a new proccess).
private void Message_Refresh_Click(object sender, EventArgs e)
{
if (!RefreshDialogs)
{
RefreshDialogs = true;
if (threadBackgroundDialogs.WorkerSupportsCancellation)
{
threadBackgroundDialogs.CancelAsync();
}
if (!threadBackgroundDialogs.IsBusy)
{
downloadedDialogs = 0;
threadBackgroundDialogs = new BackgroundWorker();
threadBackgroundDialogs.WorkerSupportsCancellation = true;
threadBackgroundDialogs.DoWork += LoadDialogs;
threadBackgroundDialogs.RunWorkerCompleted += ProcessCompleted;
threadBackgroundDialogs.RunWorkerAsync();
}
}
}
void ProcessCompleted(object sender, RunWorkerCompletedEventArgs e)
{
RefreshDialogs = false;
}

So you want to keep the second process running while the first works, but they shouldn't disturb each other? And after the first one finishes the second one continues?
Crude way: While loop:
if (!RefreshDialogs)
{
RefreshDialogs = true;
this becomes:
while(RefreshDialogs)
{
}
RefreshDialogs = true;
After you set it false the second process wwill jump out of the while. (Note this is extremly inefficent since both processes will be running all the time, i'm pretty sure the second one will block the first one, but with multitasking now it shouldn't, if it block use a Dispatcher.Thread)
Elegant way: Use A Semaphore
http://msdn.microsoft.com/de-de/library/system.threading.semaphore%28v=vs.80%29.aspx
If you find it impossible to have both processes running at the same time, or want another way:
Add an Array/List/int and when the second process notices there is the first process running, like with your bool, increase your Added variable, and at the end of the process, restart the new process and decrese the variable:
int number;
if (!RefreshDialogs)
{
RefreshDialogs = true;
your code;
if(number > 0)
{
number--;
restart process
}
}
else
{
number++;
}
I have to admit, i like my last proposal the most, since its highly efficent.

Make your thread blocking. That is easy;
lock(someSharedGlobalObject)
{
Do Work, Exit early if cancelled
}
This way other threads will wait until the first thread releases the lock. They will never execute simultaneously and silently wait until they can continue.
As for other options; why not disable the button when clicked and re-enable it when the backgroundworker completes. Only problem is this does not allow for cancelling the current thread. The user has to wait for it to finish. It does make any concurrency go away very easily.

How about this approach?
Create a request queue or counter which will be incremented on every button click. Every time that count is > 0. Start the background worker. When the information comes, decrement the count and check for 0. If its still > 0 restart the worker. In that your request handler becomes sequential.
In this approach you may face the problem of continuous reference of the count by two threads, for that you may use a lock unlock condition.
I hav followed this approach for my app and it works well, hope it does the same for you.

I'm not an Windows Phone expert, but as I see it has support for TPL, so following code would read nicely:
private object syncRoot =new object();
private Task latestTask;
public void EnqueueAction(System.Action action)
{
lock (syncRoot)
{
if (latestTask == null)
latestTask = Task.Factory.StartNew(action);
else
latestTask = latestTask.ContinueWith(tsk => action());
}
}

Use can use semaphores
class TheClass
{
static SemaphoreSlim _sem = new SemaphoreSlim (3);
static void Main()
{
for (int i = 1; i <= 5; i++)
new Thread (Enter).Start (i);
}
static void Enter (object name)
{
Console.WriteLine (name + " wants to enter");
_sem.Wait();
Console.WriteLine (name + " has entered!");
Thread.Sleep (1000 * (int) name );
Console.WriteLine (name + " is leaving");
_sem.Release(); }
}
}

I found the solution and thanks to #Giedrius. Flag RefreshingDialogs is set to true only when proccess is at the end, when I added items to Listbox. The reason why I'am using this flag is that state of process changes to complete when the asynchronous operation of getting content from network(HttpWebRequest, method BeginGetRequestStream) begins, but after network operaion is complete I need to make UI operations and not only them(parse content and add it to Listbox)My solution is:
private object syncRoot = new object();
private Task latestTask;
public void EnqueueAction(System.Action action)
{
lock (syncRoot)
{
if (latestTask == null)
{
downloadedDialogs = 0;
latestTask = Task.Factory.StartNew(action);
}
else if(latestTask.IsCompleted && !RefreshingDialogs)
{
RefreshingDialogs = true;
downloadedDialogs = 0;
latestTask = Task.Factory.StartNew(action);
}
}
}
private void Message_Refresh_Click(object sender, EventArgs e)
{
Action ac = new Action(LoadDialogs2);
EnqueueAction(ac);
}

How to update a text box continously without halting the button in windows form application C#?

I need to update my text box continuously after clicking the button but the button should perform its remaining task as it is.
simple is that when click event is performed then Text box should not wait for the completion of click event but to start updating its text continuously.
sample code
using System.threading;
namespace name
{
public class sA
{
public void th()
{
textbox.invoke(new MethodInvoke(()=> textbox.AppendText("hello\n")));
}
private void Button1Click(object sender, EventArgs e)
{
thread cThread=new thread(th);
cThread.start();
while(true)
{
// do any thing
}
}
}
}
Important :: when it performs the event " Cthread.start();" text box should immediately start updating the text while the remaining functions of click event like "while loop" should perform in parallel.

IF this is inside Windows Forms.. then add Application.DoEvents(); anywhere in the loop
e.g.
private void Button1Click(object sender, EventArgs e)
{
thread cThread=new thread(th);
cThread.start();
while(true)
{
// do any thing
textbox.Invalidate();
Application.DoEvents(); // Releases the current thread back to windows form
// NOTE Thread sleep different in Application.DoEvents();
//Application.DoEvents() is available only in System.Windows.Forms
}
}
Hope this help you although late.. :)

Your while(true) block has to happen on another thread as well.
Right now its blocking the UI thread from performing any updates.
Method th() is running on a background thread but the call to Invoke can't run until the UI thread is available again.

If I understood your question correctly, you need to keep updating the TextBox's text while the button click procedure is running inside it's "while" loop. You didn't really specify where will the textbox be updated from, but I will assume that it is coming from the code inside your "while" loop.
As "akatakritos" has stated, your while loop inside the button click is the reason why your application is halting. That happens because the while loop is blocking the User Interface (UI) Thread.
What you should be doing is moving the code inside your "while" loop to run inside a different thread, and use the button click to start this new thread.
Here is a way to do this, maybe not the best, but it will do what you need:
Create a new class:
public class ClassWithYourCode
{
public TextBox TextBoxToUpdate { get; set; }
Action<string> updateTextBoxDelegate;
public ClassWithYourCode()
{ }
public void methodToExecute()
{
bool IsDone = false;
while (!IsDone)
{
// write your code here. When you need to update the
// textbox, call the function:
// updateTextBox("message you want to send");
// Below you can find some example code:
for (int i = 0; i < 10; i++)
{
Thread.Sleep(1000);
updateTextBox(string.Format("Iteration number: {0}", i));
}
// Don't forget to set "IsDone" to "true" so you can exit the while loop!
IsDone = true;
}
updateTextBox("End of method execution!");
}
private void updateTextBox(string MessageToShow)
{
if (TextBoxToUpdate.InvokeRequired)
{
updateTextBoxDelegate = msgToShow => updateTextBox(msgToShow);
TextBoxToUpdate.Invoke(updateTextBoxDelegate, MessageToShow);
}
else
{
TextBoxToUpdate.Text += string.Format("{0}{1}", MessageToShow, Environment.NewLine);
}
}
}
and, inside your button1_Click method, you can add the following code:
private void button1_Click(object sender, EventArgs e)
{
ClassWithYourCode myCode = new ClassWithYourCode();
myCode.TextBoxToUpdate = textBox1;
Thread thread = new Thread(myCode.methodToExecute);
thread.Start();
}
Now, your "while" loop is executing inside a new thread and, whenever you need to update the textbox, you do so from the UI thread, because you cannot update Windows Forms controls from a thread other than the UI thread.

Pause and Resume a Thread

I have this code to pause and resume a thread:
public partial class frmMain : Form
{
(...)
ManualResetEvent wait_handle = new ManualResetEvent(true);
(...)
}
private void frmMain_Shown(object sender, EventArgs e)
{
ThreadPool.QueueUserWorkItem(new WaitCallback(TheLoop));
}
private void TheLoop(object stateinfo)
{
bool hasInfo = true;
while (doLoop)
{
wait_handle.WaitOne();
bool hasLines = GetInfo();
if (hasLines)
{
//Consuming time Operation 1
System.Threading.Thread.Sleep(7000);
if (CurrentLine < line.Count - 1)
CurrentLine++;
else
{
bool hasInfo2 = GetInfo2();
if (hasInfo2)
{
//Consuming time Operation 2
System.Threading.Thread.Sleep(7000);
}
CurrentLine = 0;
}
}
else
System.Threading.Thread.Sleep(40000); //Wait to query again
}
}
private void btnPauseResume_Click(object sender, EventArgs e)
{
if (btnPauseResume.Text == "Pause")
{
btnPauseResume.Text = "Resume";
wait_handle.Reset();
}
else
{
btnPauseResume.Text = "Pause";
wait_handle.Set();
}
}
The code above shows a cycle information, it works find to pause and resume the "first consuming time operation" but doesn't work for the second one, if I press the button to pause the thread in the second consuming time operation, this one continues and when the first one appears again, then it pauses there.
What am I missing here?
Thx

Have you considered using a Background Worker instead since you are using WinForms? It would probably be easier than trying to 'Pause' a thread. You can check the CancellationPending property to see if a user has elected to cancel the operation. The link has a good sample to look at.

I have never seen someone pausing a thread. Create a delegate and event inside the class or method that you are executing on a separate threat. Execute that event whenever you wish to pause your thred.

There is not any reason that I can see that would prevent a second call to WaitOne from working if placed before the 2nd time consuming operation. Since you are using a ManualResetEvent the wait handle's state will persist until either Set or Reset is called. That means if you resume the thread by calling Set then both calls to WaitOne will pass through. Likewise, if you pause the thread by calling Reset then both calls to WaitOne will block. Of course, it will not be possible to predict where the worker thread will pause if there is more than one call to WaitOne.

Got it guys! the thing is where you put the WaitOne(). For instance, if I have a While Loop (like my example) if I put the wait before it, no matter how many times I hit the pause button, it won't stop the thread, it's logic since the loop already began, but if I put it at the end, then it will work.
Appreciated your help.