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Button hangs with infinite loop [duplicate]

This question already has answers here:
WinForm Application UI Hangs during Long-Running Operation
(3 answers)
Closed 6 years ago.
if I start my C# Windows Form Application, buttons hangs, because it is endless cycle. I want to see the change of variable value from button2 click into infinite loop of button1 through the global variable
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace XX_5
{
public partial class Form1 : Form
{
private int g;
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
int i = 0;
for (;;)
{
textBox1.AppendText("ID: [" + i++ + "] Variable value: [" + g + "]\n");
}
}
private void button2_Click(object sender, EventArgs e)
{
g = 1;
}
}
}

If you keep the infinite-loop in the button-click event handler, your application hangs definitely, since windows can't get / dispatch /process messages any more.
You can fix like the following:
private void button1_Click(object sender, EventArgs e)
{
int i = 0;
textBox1.AppendText("ID: [" + i++ + "] Variable value: [" + g + "]\n");
}
private void button2_Click(object sender, EventArgs e)
{
// int g = 1; // here you declare a local variable
g = 1; // use the member variable instead
}

Take a look at the Timer control (under the Components tab in the toolbox). You can put your code (without the for loop) in there and it will run every x milliseconds with the benefit that it will not hang. You will need to define your i variable at the form level when you do this. Your timer can then access this 'global variable'.
Something like this...
public partial class Form1 : Form
{
private int i = 0;
private int g = 0;
public Form1()
{
InitializeComponent();
}
private void button2_Click(object sender, EventArgs e)
{
g = 1;
}
private void timer1_Tick(object sender, EventArgs e)
{
textBox1.AppendText("ID: [" + i++ + "] Variable value: [" + g + "]\n");
}
private void Form1_Load(object sender, EventArgs e)
{
timer1.Enabled = true;
}
}

Application is not responding

What the application should do
This application should take the input of time (seconds, minutes and hours) and shutdown the computer after that time. It should also update the text box with how long left until the computer has shut down.
What the application actually does
I had an issue that I 'fixed' where the called ac across threads weren't safe, so I fixed it and I don't get that error now. However, the updateThread doesn't update and print the time left; and the text box doesn't get "test" appended to it. The UI also becomes Not Responding. Any help would be much appreciated.
Also, if you see anything else that could be done better, please comment and explain. Thanks!
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace ShutdownPC
{
public partial class Form1 : Form
{
int inputHours;
int inputMinutes;
int inputSeconds;
Thread sleepingThread;
Thread updatingThread;
NotifyIcon shutdownPCIcon;
Icon defaultIcon;
public Form1()
{
InitializeComponent();
defaultIcon = new Icon("defaultIcon.ico");
shutdownPCIcon = new NotifyIcon();
shutdownPCIcon.Icon = defaultIcon;
shutdownPCIcon.Visible = true;
MenuItem progNameMenuItem = new MenuItem("ShutdownPC by Conor");
MenuItem breakMenuItem = new MenuItem("-");
MenuItem quitMenuItem = new MenuItem("Quit");
ContextMenu contextMenu = new ContextMenu();
contextMenu.MenuItems.Add(progNameMenuItem);
contextMenu.MenuItems.Add(breakMenuItem);
contextMenu.MenuItems.Add(quitMenuItem);
shutdownPCIcon.ContextMenu = contextMenu;
shutdownPCIcon.Text = "ShutdownPC";
quitMenuItem.Click += QuitMenuItem_Click;
}
private void QuitMenuItem_Click(object sender, EventArgs e)
{
shutdownPCIcon.Dispose();
sleepingThread.Abort();
updatingThread.Abort();
this.Close();
}
public void sleepThread()
{
if (this.InvokeRequired)
{
this.Invoke(new MethodInvoker(sleepThread));
}
else {
textBox1.Enabled = false;
textBox2.Enabled = false;
textBox3.Enabled = false;
button1.Enabled = false;
int totalMilliseconds = ((inputHours * 3600) + (inputMinutes * 60) + inputSeconds) * 1000;
Thread.Sleep(totalMilliseconds);
//Process.Start("shutdown", "/s /t 0");
richTextBox1.AppendText(String.Format("test"));
}
}
public void updateThread()
{
if (this.InvokeRequired)
{
this.Invoke(new MethodInvoker(updateThread));
}
else {
int totalSeconds = (inputHours * 3600) + (inputMinutes * 60) + inputSeconds;
while (totalSeconds > 0)
{
TimeSpan time = TimeSpan.FromSeconds(totalSeconds);
string timeOutput = time.ToString(#"hh\:mm\:ss");
richTextBox1.AppendText(String.Format(timeOutput));
Thread.Sleep(1000);
richTextBox1.Clear();
totalSeconds--;
}
}
}
private void textBox1_TextChanged(object sender, EventArgs e)
{
inputHours = Convert.ToInt32(textBox1.Text);
inputHours = int.Parse(textBox1.Text);
}
private void textBox2_TextChanged(object sender, EventArgs e)
{
inputMinutes = Convert.ToInt32(textBox2.Text);
inputMinutes = int.Parse(textBox2.Text);
}
private void textBox3_TextChanged(object sender, EventArgs e)
{
inputSeconds = Convert.ToInt32(textBox3.Text);
inputSeconds = int.Parse(textBox3.Text);
}
private void button1_Click(object sender, EventArgs e)
{
updatingThread = new Thread(new ThreadStart(updateThread));
updatingThread.Start();
sleepingThread = new Thread(new ThreadStart(sleepThread));
sleepingThread.Start();
}
private void richTextBox1_TextChanged(object sender, EventArgs e)
{
}
}
}

Using Invoke in the beginning of method that runs in separate thread is bad idea, because all code runs in GUI thread and lock it.
You should Invoke only GUI updating code!!!

How to display a text on a RichTextBox char by char?

I have Form1, RichTextBox1 and Button1 on my Form
To understand what i'm trying to do; take a look at this link, type in a facebook profile link and click on Hack Account AND SEE THE GREEN TEXT THAT APPEARS
I'm using the code below in C# to achieve what i want to do :
private void button1_Click(object sender, EventArgs e)
{
string myStr = "This is a test string to stylize your RichTextBox1";
foreach (char c in myStr.ToCharArray()) {
Thread.Sleep(100);
richTextBox1.AppendText(c.ToString());
}
}
But it doesn't work, the text appears in the text box at one time; Not char by char!

The reason your code is showing all the text at once is using Thread.Sleep() keep the main Thread (the UI thread) suspended / sleep mode, so none of the Application message are processed on form & the form paint / drawing event are not doing the job as the UI thread is sleeping/suspended!
Solution 1: Use a helper Thread so that Thread.Sleep() dont make ur app go in non-responsive mode
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
string myStr = "This is a test string to stylize your RichTextBox1";
ThreadPool.QueueUserWorkItem(ShowTextInInterval, myStr);
}
private void ShowTextInInterval(object state)
{
string mystr = state as string;
if (mystr == null)
{
return;
}
for (int i = 0; i < mystr.Length; i++)
{
AppendNewTextToRichTextBox(mystr[i]);
Thread.Sleep(100);
}
}
private delegate void app_char(char c);
private void AppendNewTextToRichTextBox(char c)
{
if (InvokeRequired)
{
Invoke(new app_char(AppendNewTextToRichTextBox), c);
}
else
{
richTextBox1.AppendText(c.ToString(CultureInfo.InvariantCulture));
}
}
}
Solution # 2 : Use a timer
public partial class Form1 : Form
{
private Timer tbTimer = new Timer();
string myStr = "This is a test string to stylize your RichTextBox1";
private int charPos = 0;
public Form1()
{
InitializeComponent();
tbTimer.Interval = 100;
tbTimer.Tick += TbTimerOnTick;
}
private void TbTimerOnTick(object sender, EventArgs eventArgs)
{
if (charPos < myStr.Length - 1)
{
richTextBox1.AppendText(myStr[charPos++].ToString(CultureInfo.InvariantCulture));
}
else
{
tbTimer.Enabled = false;
}
}
private void button1_Click(object sender, EventArgs e)
{
tbTimer.Enabled = true;
}
}

This is because the textbox is not refreshing whilst you are still running your code. Try putting this:
foreach (char c in myStr.ToCharArray()) {
Thread.Sleep(100);
richTextBox1.AppendText(c.ToString());
richTextBox1.Refresh();
}

The problem you are having is not in appending the text,
richTextBox1.AppendText(c.ToString()); //Good
works as expected but the issue is that you are putting the UI thread to sleep blocking the drawing of the text on the Rich Text Box.
Thread.Sleep(100); //Not so good
A quick workaround would be to add
richTextBox1.Refresh();
This forces the control to be redrawn after appending the text, but note your entire UI is still going to be frozen while the thread sleeping. A better solution maybe to use a System.Windows.Forms.Timer to accomplish your goal. This class triggers an event every specified interval. Some quick code,
private System.Windows.Forms.Timer TextUpdateTimer = new System.Windows.Forms.Timer();
private string MyString = "This is a test string to stylize your RichTextBox1";
private int TextUpdateCount = 0;
private void button1_Click(object sender, EventArgs e)
{
//Sets the interval for firing the "Timer.Tick" Event
TextUpdateTimer.Interval = 100;
TextUpdateTimer.Tick += new EventHandler(TextUpdateTimer_Tick);
TextUpdateCount = 0;
TextUpdateTimer.Start();
}
private void TextUpdateTimer_Tick(object sender, EventArgs e)
{
//Stop timer if reached the end of the string
if(TextUpdateCount == MyString.Length) {
TextUpdateTimer.Stop();
return;
}
//AppendText method should work as expected
richTextBox1.AppendText(MyString[TextUpdateCount].ToString());
TextUpdateCount++;
}
This updates the text box char by char without blocking the main thread and maintains usability on the front end.

Passing argument into backgroundWorker (for use as a Cancel button)

I'm new to C# and object-oriented programming in general. I've been trying to implement a "Cancel" button into my GUI so that the user can stop it mid-process.
I read this question: How to implement a Stop/Cancel button? and determined that a backgroundWorker should be a good option for me, but the example given doesn't explain how to hand arguments to the backgroundWorker.
My problem is that I do not know how to pass an argument into backgroundWorker such that it will stop the process; I have only been able to get backgroundWorker to stop itself.
I created the following code to try to learn this, where my form has two buttons (buttonStart and buttonStop) and a backgroundWorker (backgroundWorkerStopCheck):
using System;
using System.ComponentModel;
using System.Windows.Forms;
using System.Threading;
using System.Timers;
namespace TestBackgroundWorker
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
// Set the background worker to allow the user to stop the process.
backgroundWorkerStopCheck.WorkerSupportsCancellation = true;
}
private System.Timers.Timer myTimer;
private void backgroundWorkerStopCheck_DoWork(object sender, DoWorkEventArgs e)
{
//If cancellation is pending, cancel work.
if (backgroundWorkerStopCheck.CancellationPending)
{
e.Cancel = true;
return;
}
}
private void buttonStart_Click(object sender, EventArgs e)
{
// Notify the backgroundWorker that the process is starting.
backgroundWorkerStopCheck.RunWorkerAsync();
LaunchCode();
}
private void buttonStop_Click(object sender, EventArgs e)
{
// Tell the backgroundWorker to stop process.
backgroundWorkerStopCheck.CancelAsync();
}
private void LaunchCode()
{
buttonStart.Enabled = false; // Disable the start button to show that the process is ongoing.
myTimer = new System.Timers.Timer(5000); // Waste five seconds.
myTimer.Elapsed += new ElapsedEventHandler(myTimer_Elapsed);
myTimer.Enabled = true; // Start the timer.
}
void myTimer_Elapsed(object sender, ElapsedEventArgs e)
{
buttonStart.Enabled = true; // ReEnable the Start button to show that the process either finished or was cancelled.
}
}
}
The code, if it worked properly, would just sit there for five seconds after the user clicked "Start" before re-enabling the Start button, or would quickly reactivate the Start button if the user clicked "Stop".
There are two problems with this code that I am not sure how to handle:
1) The "myTimer_Elapsed" method results in an InvalidOperationException when it attempts to enable the Start button, because the "cross-thread operation was not valid". How do I avoid cross-thread operations?
2) Right now the backgroundWorker doesn't accomplish anything because I don't know how to feed arguments to it such that, when it is canceled, it will stop the timer.
I'd appreciate any assistance!

First of all, the problem to avoid "cross-thread operation was not valid" is use Invoke on controls. You cannot use a control from a different thread.
About the second issue, I would implement it in the following way. This is a minimum background worker implementation with cancel support.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
namespace WindowsFormsApplication5
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
// Set the background worker to allow the user to stop the process.
backgroundWorkerStopCheck.WorkerSupportsCancellation = true;
backgroundWorkerStopCheck.DoWork += new DoWorkEventHandler(backgroundWorkerStopCheck_DoWork);
}
private void backgroundWorkerStopCheck_DoWork(object sender, DoWorkEventArgs e)
{
try
{
for (int i = 0; i < 50; i++)
{
if (backgroundWorkerStopCheck.CancellationPending)
{
// user cancel request
e.Cancel = true;
return;
}
System.Threading.Thread.Sleep(100);
}
}
finally
{
InvokeEnableStartButton();
}
}
private void buttonStart_Click(object sender, EventArgs e)
{
//disable start button before launch work
buttonStart.Enabled = false;
// start worker
backgroundWorkerStopCheck.RunWorkerAsync();
}
private void buttonStop_Click(object sender, EventArgs e)
{
// Tell the backgroundWorker to stop process.
backgroundWorkerStopCheck.CancelAsync();
}
private void InvokeEnableStartButton()
{
// this method is called from a thread,
// we need to Invoke to avoid "cross thread exception"
if (this.InvokeRequired)
{
this.Invoke(new EnableStartButtonDelegate(EnableStartButton));
}
else
{
EnableStartButton();
}
}
private void EnableStartButton()
{
buttonStart.Enabled = true;
}
}
internal delegate void EnableStartButtonDelegate();
}
About passing arguments to the worker, you can pass any object in the RunWorkerAsync() method, and its reveived in the backgroundWorkerStopCheck_DoWork method:
...
backgroundWorkerStopCheck.RunWorkerAsync("hello");
...
private void backgroundWorkerStopCheck_DoWork(object sender, DoWorkEventArgs e)
{
string argument = e.Argument as string;
// argument value is "hello"
...
}
Hope it helps.

try this example and you will see how to pass data to and from the BackgroundWorker:
public partial class Form1 : Form
{
BackgroundWorker bw = new BackgroundWorker();
public Form1()
{
InitializeComponent();
bw.DoWork += new DoWorkEventHandler(bw_DoWork);
bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);
bw.WorkerSupportsCancellation = true;
}
private void button1_Click(object sender, EventArgs e)
{
btnStart.Enabled = false;
btnCancel.Enabled = true;
double[] data = new double[1000000];
Random r = new Random();
for (int i = 0; i < data.Length; i++)
data[i] = r.NextDouble();
bw.RunWorkerAsync(data);
}
void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
btnStart.Enabled = true;
btnCancel.Enabled = false;
if (!e.Cancelled)
{
double result = (double)e.Result;
MessageBox.Show(result.ToString());
}
}
void bw_DoWork(object sender, DoWorkEventArgs e)
{
double[] data = (double[])e.Argument;
for (int j = 0; j < 200; j++)
{
double result = 0;
for (int i = 0; i < data.Length; i++)
{
if (bw.CancellationPending)
{
e.Cancel = true;
return;
}
result += data[i];
}
e.Result = result;
}
}
private void btnCancel_Click(object sender, EventArgs e)
{
bw.CancelAsync();
btnStart.Enabled = true;
btnCancel.Enabled = false;
}
}

Visual C# Windows Form Textbox Not Auto-updating

I'm attempting to code an application that reads in the values from an IMU. I'm trying to get the different values of the attitude (i.e. direction) of the IMU for 1 second when using the getAtr_Click method. However, while this is calling the Get_Attitude function, it only changes the textbox values once on my form. How do I make it change each time? (I want to see 10 different values flash by on the textbox).
Here's my code:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;
using System.Timers;
using VectorNav.Devices;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
public static Vn100 vn100 = new Vn100("COM5", 9600);
// New Vn100 on COM5
private void Get_Attitude()
//gets the current yaw, pitch, roll in degrees, and displays
{
var attitude = vn100.CurrentAttitude;
yaw.Text = Convert.ToString(attitude.Ypr.YawInDegs);
pitch.Text = Convert.ToString(attitude.Ypr.PitchInDegs);
roll.Text = Convert.ToString(attitude.Ypr.RollInDegs);
}
public Form1()
//connect to the Vn100, set its output to YPR, output at 10Hz
{
InitializeComponent();
vn100.Connect();
vn100.SetAsyncDataOutputType(Vn100.AsyncOutputType.Ypr, true);
vn100.SetAsyncDataOutputFreq(10, true);
}
private void Form1_Load(object sender, EventArgs e)
{
Get_Attitude();
}
private void tare_Click(object sender, EventArgs e)
{
vn100.Tare(true);
vn100.Tare(true); //for some reason it doesn't display the correct Attitude values w/out a double Tare
Get_Attitude();
}
private void getAtr_Click(object sender, EventArgs e)
{
for (int i = 1; i <= 10; i++)
{
while (vn100.CurrentAttitude == null)
Thread.Sleep(10);
Get_Attitude();
}
}
protected override void OnFormClosing(FormClosingEventArgs e)
//disconnect from the Vn100 when the box is closed
{
vn100.Disconnect();
base.OnFormClosing(e);
}
}
}

This is because you are haulting the UI thread:
private void getAtr_Click(object sender, EventArgs e)
{
for (int i = 1; i <= 10; i++)
{
while (vn100.CurrentAttitude == null)
Thread.Sleep(10); // < - UI can't respond in a sleep
Get_Attitude();
}
}
You could do this:
private void getAtr_Click(object sender, EventArgs e)
{
for (int i = 1; i <= 10; i++)
{
while (vn100.CurrentAttitude == null)
{
Thread.Sleep(10); // < - UI can't respond in a sleep
Application.DoEvents();
}
Get_Attitude();
}
}
Or you could force the update to happen synchronously:
private void tare_Click(object sender, EventArgs e)
{
vn100.Tare(true);
vn100.Tare(true); //for some reason it doesn't display the correct Attitude values w/out a double Tare
Get_Attitude();
this.Update();
}
Or you could use a timeout to update the form instead of a loop.
private void tare_Click(object sender, EventArgs e)
{
System.Windows.Forms.Timer myTimer = new System.Windows.Forms.Timer();
myTimer.Tick += new EventHandler(TimerEventProcessor);
myTimer.Interval = 10;
myTimer.Start();
}
void TimerEventProcessor(object sender, EventArgs e)
{
Get_Attitude();
}

Do you want to see 10 (possibly) different values displayed in your textboxes during 1s, at an interval of 10ms, once you call getAttr_Click()?
If yes, then that would be the way to do it:
private void getAtr_Click(object sender, EventArgs e)
{
for (int i = 1; i <= 10; i++)
{
while (vn100.CurrentAttitude == null)
Thread.Sleep(10);
Get_Attitude();
Thread.Sleep(10);
}
}
In your version, the thread that called the getAttr_Click() method just checks vn100.CurrentAttutude at 10ms intervals. Once that has a non-null value, I suspect it remains non-null, meaning your while() loop will be skipped in every for() iteration so Get_Attitude() will be called 10 times in a row (probably) so fast that you only get to see the last values on the screen.
Thing is, this will keep your UI unresponsive each 10ms during the click, so you might consider calling this getAtr_Click() asynchronously or other trivial solution.
EDIT: Actually, it would help knowing the behaviour of the vn100 component. In the case it is unpredictable, the only thing you can be sure of is displaying 10 different values at no less than 10ms distance in time, regardless if you do everything on the UI thread or on a different thread. It is all related to that vn100.CurrentAttitude behaviour...

change it to:
private void Get_Attitude()
//gets the current yaw, pitch, roll in degrees, and displays
{
var attitude = vn100.CurrentAttitude;
yaw.Text = Convert.ToString(attitude.Ypr.YawInDegs);
pitch.Text = Convert.ToString(attitude.Ypr.PitchInDegs);
roll.Text = Convert.ToString(attitude.Ypr.RollInDegs);
vn100.CurrentAttitude = null;
}
private void getAtr_Click(object sender, EventArgs e)
{
for (int i = 1; i <= 10; i++)
{
while (vn100.CurrentAttitude == null)
Thread.Sleep(10);
Get_Attitude();
Application.DoEvents();
}
}