I am trying to update a textbox using the code behind in an ASP application like this:
protected void click_handler(object sender, EventArgs e)
{
Thread worker = new Thread(new ThreadStart(thread_function));
worker.Start();
}
protected void thread_function()
{
int i = 0;
while(true)
{
Textbox.Text = i.ToString();
i++;
}
}
The textbox shows one variable the first time but it doesn't get updated after that, what am I doing wrong? I searched and people are suggestin calling Textbox.Update or Textbox.Refresh but I think these are old as they don't exist anymore.
Thanks
You can't use server side code to update client side values in this manner. Anyway, you seem to be missing some kind of pause (e.g. Thread.Sleep) as currently your loop will run wildly out of control.
You need to look into using client side scripting (I.e. JavaScript) along with something like setTimeout:
https://developer.mozilla.org/en/docs/Web/API/window.setTimeout
Here's an example:
http://jsfiddle.net/PXN9K/
Apologies for the poor formatting and slightly lazy naming/refactoring, but I'm doing this on my phone.
Here's the code from the fiddle, copied here for future posterity.
var i = 0;
var updateTextbox =function()
{ document.getElementById('textbox').value = '' + i; }
var update = function() {
window.setTimeout(function() {
i++;
updateTextbox();
update();
}, 1000);
};
updateTextbox();
update();
Related
Im trying to make a simple application to learn some things in c# (Visual Studio).
For now i am building a music player, and one of the actions is fading out the music at the button click event.
I've got no problem with building a fade-out part, i made a while loop and put the volume down with 1% eacht time the loop is running. Also i update a label with the fade value.
Only problem is, for slowing down the fading i'm using the Thread.Sleep event, and that part is freezing my application, and also is blocking any updates to my text label with the fade value.
The fading is working fine, so the only part I have to work on is another option to build some delay in. On some topics over here i did read about the timer, and i added a timer component in Visual Studio. Only problem, I am new to c# and don't know how to use it correctly in this while loop.
Can anybody give me some help?
The current code is:
private void BtnPodiumtune1Fadeout_Click(object sender, EventArgs e)
{
PlayerPodiumtune1.settings.volume = 100;
fade1 = 100;
while (fade1 != -1)
{
PlayerPodiumtune1.settings.volume = fade1;
Fadelevel1.Text = fade1.ToString();
System.Threading.Thread.Sleep(30);
fade1 = fade1 - 1;
}
PlayerPodiumtune1.Ctlcontrols.stop();
}
You could use a pattern like this instead of a timer. A timer is a fine way to go, just throwing this option out there:
private async void button_Click(object sender, EventArgs e)
{
if (Monitor.TryEnter(sender))
{
int fade1 = 1000;
while (fade1 != -1)
{
await Task.Delay(30);
fade1--;
}
}
}
So sender is the button, and Monitor.TryEnter prevents the function from being run again until the function is done. async tells the framework that this function can be executed asynchronously and is necessary for await. await returns control of the thread to the UI until the task is done.
PS--You're going to need something like Monitor.TryEnter to prevent re-entrancy in a timer-based solution as well, by the way.
This is a Console Application in C#:
using System;
namespace WaitAsync
{
class Program
{
static void Main(string[] args)
{
bool ok = false;
Console.Write("EnterTime (Seconds): ");
int time = Convert.ToInt32(Console.ReadLine()) * 1000;
while (ok != true)
{
System.Threading.Thread.Sleep(time);
ok = true;
Console.WriteLine("Waiting Time Just Finished");
}
Console.ReadLine();
}
}
}
We are learning multi-threadding today in class and we came across a very curious error. When doing a for loop in our new thread the upper bound of the for loop keeps getting passed. The thread is being killed but then another value will appear and end another thread.
For the purpose of debugging the error I changed the upper bound to 90 to avoid the OutOfRange Exception on the progressbar.
While outputting the counter to the progressing bar and updating the progress bar I got this in my output window.
If i commented out the updating on the progress bar (pbLoad.Value = i;) I got this in my output window
I have tried changing the loop to i<101 and also tried moving where the i++ was but it made no difference
EDIT: This is coming from the BeginInvoke. When i switched it to Invoke it worked but then I will get a deadlock when trying to use the cancel button.
Here is the code:
public partial class Form1 : Form
{
Thread backgroundThread;
bool stopExecution = false;
public Form1()
{
InitializeComponent();
}
private void btnStart_Click(object sender, EventArgs e)
{
stopExecution = false;
btnStart.Enabled = false;
backgroundThread = new Thread(DoDomethingThatTakesAWhile);
backgroundThread.Start();
}
private void DoDomethingThatTakesAWhile()
{
for (int i = 0; i <= 100; i++)
{
if (!stopExecution)
{
Thread.Sleep(100);
if (pbLoad.InvokeRequired)
{
MethodInvoker myMethod
= new MethodInvoker(
delegate
{
if (!stopExecution)
{
pbLoad.Value = i;
Debug.WriteLine(i); //i to output window
}
});
pbLoad.BeginInvoke(myMethod);
}
else
{
pbLoad.Value = i;
}
}
else
{
break;
}
}
}
private void btnCancel_Click(object sender, EventArgs e)
{
//backgroundThread.Abort();
stopExecution = true;
backgroundThread.Join();
pbLoad.Value = 0;
btnStart.Enabled = true;
}
}
When you call MethodInvoke it will not occurs at that moment, but some time later.
In your scenario you have a chance of following to occurs:
invoked code is finally executed;
the loop is already finished (and i become 101)
you are accessing i directly and you read 101.
And to fix it you can make a copy of i (by passing it as a parameter to invoked method):
pbLoad.BeginInvoke(new Action<int>(a =>
{
if (!stopExecution)
{
pbLoad.Value = a;
Debug.WriteLine(a); //a to output window
}
}), new object[] { i });
P.S: you don't need to check for InvokeRequired, unless you plan to call DoDomethingThatTakesAWhile method directly, which I assume is not the case.
You're using BeginInvoke which explicitly opens the possibility for races. I recommend synchronous invoking.
Furthermore, you are capturing i, not its value. This is racy and only works by accident because you're sleeping.
Either of the changes will fix the problem. Do both of them.
If you can, abolish this low-level use of synchronization and use async/await.
public partial class _Default : System.Web.UI.Page
{
private static Stopwatch timer = new Stopwatch();
Thread timeThread = new Thread(timeKeeper);
private static int min = 0, sec = 0;
protected void Page_Load(object sender, EventArgs e)
{
}
protected void startstop_Click(object sender, EventArgs e)
{
timeThread.Start();
if(timer.IsRunning()) {timer.Stop}
else timer.Start();
}
private static void timeKeeper()
{
while (timer.IsRunning)
{
mydelegate();
}
}
private static void mydelegate()
{
_Default temp = new _Default();
temp.Update();
}
private void Update()
{
min = timer.Elapsed.Minutes;
sec = timer.Elapsed.Seconds;
time.Text = min + ":" + sec;
}
}
what i want to do is have a button that controls the a stopwatch, when you click it it starts, click it again it stops. I figured the best way to do it is with a thread if i want the time.text display to continue update and to be able to click the button still. when i run the above program it gets to time.text = min + ":" + sec; and throws a nullreferenceexception. Any help on how to fix this would be greatly appreciated. I am semi new to programming in C#/asp.net.
Is there a better way of working with delegates then this. I have spent hours looking up how to use them with not many usual/easy to understand tutorials or blogs
I'm not sure where to begin.
Remember you are programming a webpage, and every call to a server result in a new webpage life cycle on the server. So using threads in a webpage will not result in the correct behaviour.
To get the kind of behaviour you want, you'll have to do the timer and click handling on the client instead of the server. You can use jQuery to facilitate in this. One other option is to use ajax if you have to keep the server up-to-date.
It seems that the problem is here:
_Default temp = new _Default();
The new class isn't passing through the ASP.Net pipeline, so when you try to update a control in the markup (time), it has not actually loaded.
I think your approach here is a bit flawed. If you want to do it on the server side, you'll need to use repeated Ajax requests (or a web socket) to keep the browser in sync with the timer object on the server. Not to mention, what happens when you have multiple users and the threads start colliding? It seems like it would be far better to use Javascript.
I made a program that loads a bunch of computer information. In the Form_Load event I have it initialize 3 (that number will grow) panels of information. One that has a bunch of unit information seems to make the program load rather slowly. I've tried to speed it up a bunch by switching from WMI to using Native calls, which helped a bunch. Soon though I'm going to have network information posted as well. I used to load that panel but i disabled it for a little bit till I work out the bugs in my other panels. So while learning how I can use a seperate thread to update my battery information I figured that I might be able to create seperate threads in my unit information panel so that it might could load faster. I dont know that any of my information would cause concurrent issues, but i can work on that.
I want to start small so what if i change this
private void Form1_Load(object sender, EventArgs e)
{
unitInformationPanel1.PopulateUnitInformation();
batteryInformationPanel1.InitializeBatteries();
magStripeReaderPanel1.SetupPointOfSale();
}
to this
private void Form1_Load(object sender, EventArgs e)
{
Thread infoThread = new Thread(new ThreadStart(unitInformationPanel1.PopulateUnitInformation));
infoThread.Start();
batteryInformationPanel1.InitializeBatteries();
magStripeReaderPanel1.SetupPointOfSale();
}
would the info thread be terminated when populate unit info is done? or would it be better to move that thread creation into PopulateUnitInformation? here is what it looks like.
public void PopulateUnitInformation()
{
unitModelLabel.Text = Properties.Settings.Default.UnitModelString;
serialNumberLabel.Text = Properties.Settings.Default.UnitSerialString;
biosVersionLabel.Text = UnitBios.GetBiosNumber();
osLabel.Text = OS.getOSString();
cpuLabel.Text = UnitCpu.GetCpuInfo();
var hdd = HddInfo.GetHddInfo();
diskNameLabel.Text = hdd.Name;
diskCapacityLabel.Text = hdd.Capacity;
diskFirmwareLabel.Text = hdd.Firmware;
memoryLabel.Text = MemoryInformation.GetTotalMemory();
NetworkPresenceInformation.GetAdapatersPresent();
biometricLabel.Text = BiometricInformation.IsPresent ? "Present" : "Not Present";
var networkAdaptersPresense = NetworkPresenceInformation.GetAdapatersPresent();
bluetoothLabel.Text = networkAdaptersPresense[0] ? "Present" : "Not Present";
wifiLabel.Text = networkAdaptersPresense[1] ? "Present" : "Not Present";
cellularLabel.Text = networkAdaptersPresense[2] ? "Present" : "Not Present";
}
--
wow i just ran it with the infothread and it still took some time to load (might be the 12 panels i created in the main thread. but it loaded the 12 frames and the unit information panel populated its information after everything loaded. That was cool, but is it safe? is it somewhat easy to make 12 threads for my panels? or is that dumb?
EDIT
this is what i did for stopwatch.
Stopwatch programTimer;
public Form1()
{
programTimer = Stopwatch.StartNew();
InitializeComponent();
SetupDebugWindow();
TerminateKeymon();
UnitModel.SetModel();
UnitSerialNumber.SetSerialNumber();
}
private void Form1_Shown(object sender, EventArgs e)
{
audioBrightnessPanel1.UpdateBrightnessTrackbar();
applicationLauncherPanel1.LoadApplications();
programTimer.Stop();
Console.WriteLine("Load Time: {0}",programTimer.ElapsedMilliseconds);
timer1.Start();
}
Will this be accurate?
EDIT 2 6/18/2012
Well I took the advice of using backgroundworker. Please let me know if i did this right.
private void Form1_Load(object sender, EventArgs e)
{
backgroundWorker1.RunWorkerAsync();
}
void BackgroundWorker1DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
{
unitInformationPanel1.PopulateUnitInformation();
batteryInformationPanel1.InitializeBatteries();
magStripeReaderPanel1.SetupPointOfSale();
}
You've asked a very broad question, but I'm going to give some general advice. If you want more specific information, you should consider deleting this question and posting more specific individual questions.
First and foremost, you should very strongly consider using something like the System.Threading.Task class for your multithreaded operations. There is a ton of information online about how to get started with it and how you can use Tasks to manage asynchronous operations. The short story is that if you're spinning up your own thread (as you're doing above), you almost certainly should be using something else to do that for you.
Adding multithreading to your code will not, in the strictest sense of the word, make it any "faster"; they will always take the same amount of total processor time. What it can and will do is two things: free up the UI thread to be responsive and allow you to split that "total processor time" across multiple cores or processors, should those be available to the system. So, if you have operation X that takes 10 seconds to complete, then just shifting operation X to another thread will not make it complete any faster than 10 seconds.
No, what you are doing above is not safe. I'm assuming that somewhere you've turned off checking for cross-thread communication errors in your app? Otherwise, that code should throw an exception, assuming this is a WinForms or WPF application. This is one reason to use Tasks, as you can easily separate the part of your process that actually takes a long time (or isn't UI related), then add a task continuation that uses the results and populates the UI elements within a properly synchronized context.
So my final approach this was as follows. I felt that my Main Form was doing more than it should. Sticking with the single responsibility principle I decided that MainForm should only be responsible for one thing, showing and displaying all 12 panels (now down to 11, i turned one into a menu item). So moved all the multithreading out of mainform and into program.cs. I found that this was even a little more difficult. What I did find though was a simple solution that allows me to not even worry about multithreading at all. It was the Idle event. Here is what i chose to do.
[STAThread]
static void Main()
{
DateTime current = DateTime.Now;
DateTime today = new DateTime(2012,7,19);
TimeSpan span = current.Subtract(today);
if (span.Days<0)
{
MessageBox.Show("Please adjust Time then restart Aspects","Adjust Time");
Process.Start("timedate.cpl").WaitForExit();
}
else
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Idle += new EventHandler(Application_Idle);
mainForm = new MainForm();
mainForm.Closing += new CancelEventHandler(mainForm_Closing);
#if !DEBUG
TerminateKeymon();
StartSerial();
SetupDefaultValues();
EmbeddedMessageBox(0);
#endif
Application.Run(mainForm);
}
}
static void Application_Idle(object sender, EventArgs e)
{
Application.Idle -= Application_Idle;
mainForm.toolStripProgressBar1.Increment(1);
UnitInformation.SetupUnitInformation();
mainForm.toolStripProgressBar1.Increment(1);
Aspects.Unit.HddInfo.GetHddInfo();
mainForm.toolStripProgressBar1.Increment(1);
for (int i = 0; i < mainForm.Controls.Count; i++)
{
if (mainForm.Controls[i] is AbstractSuperPanel)
{
try
{
var startMe = mainForm.Controls[i] as AbstractSuperPanel;
startMe.StartWorking();
mainForm.toolStripProgressBar1.Increment(1);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message + mainForm.Controls[i].ToString());
}
}
}
mainForm.toolStripProgressBar1.Value = 0;
}
to sum up what that does is is I add a idle listener event. Once the thead goes idle (basically meaning that Mainform is finished drawing and making all 12 panels and is showing on my desktop) I then kill the idle event listener and tell all my panels and classes to start working one at a time, updating my progress bar as I go. It works great. The load time is still the same as it was before, but there is window visibile after only a few seconds. Maybe not the best use of resources, but i think the solution is simple and straight forward.
I had a question somewhat related to this for Mobile app development a few months back (see How to write a Trigger?), and Marc "the man" Gravell posted back with a simple class that I modified to return data to my main application whenever the thread was complete.
The actual class I put into use has loads of pointless data (for you), so I'm going to paste in a revised version of Mr. Gravell's code using techniques which I used to make them work:
First, I had to create my own EventArgs class:
public class SuperEventArgs : EventArgs {
private object data;
public SuperEventArgs(object data) : base() {
this.data = data;
}
public object Data { get { return data; } }
}
Using that, here is a class I created to pass my data back to the main thread:
public delegate event DataChangedHandler(object sender, SuperEventArgs e);
public class Simple1 {
private object parameter1, parameter2;
private Control parent;
#if PocketPC
public delegate void MethodInvoker(); // include this if it is not defined
#endif
public Simple1(Control frmControl, object param1, object param2) {
parent = frmControl;
parameter1 = param1;
parameter2 = param2;
}
public event DataChangedHandler DataChanged;
public void Start() {
object myData = new object(); // whatever this is. DataTable?
try {
// long routine code goes here
} finally {
if (DataChanged != null) {
SuperEventArgs e = new SuperEventArgs(myData);
MethodInvoker methInvoker = delegate {
DataChanged(this, e);
};
try {
parent.BeginInvoke(methInvoker);
} catch (Exception err) {
Log(err); // something you'd write
}
}
}
}
}
Back in the actual main thread of execution, you'd do something like this:
public partial class Form1 : Form {
private Simple1 simple;
public Form1() {
object query = new object(); // something you want to pass in
simple = new Simple1(this, query, DateTime.Now);
simple.DataChanged += new DataChangedHandler(simple1_DataChanged);
Thread thread = new Thread(simpleStart);
thread.Start();
}
private void simpleStart() {
if (simple != null) {
simple.Start();
}
}
private void simple1_DataChanged(object sender, SuperEventArgs e) {
MyFancyData fancy = e.Data as MyFancyData;
if (fancy != null) {
// populate your form with the data you received.
}
}
}
I know it looks long, but it works really well!
This is not anything I have actually tested, of course, because there isn't any data. If you get to working with it and you experience any issues, let me know and I'll happily help you work through them.
~JoeP
I have here a long method that takes a little while to execute. I would like to keep the user entertained so I created a progress bar and a label. What I would like is for that label to change while the system executes the progress. Ive been looking at Application.DoEvents(), but it seems like thats the wrong way to go. This application is pretty simple and its just a project and nothing professional. All this app does is send a file to a client and insert the data into a database.
I have one label (besides a success and error label), that I would like to constantly update along side the progress bar. Any ideas or tips on how to do this? Would Application.DoEvents() be acceptable in this situation? Or is there a simple way to update the text. I am using C#, asp.net, and a System.Web.UI.Page. Any help or pointing me to the right direction would be greatly appreciated.
protected void Button_Click(object sender, EventArgs e)
{
PutFTPButton.Enabled = false;
Thread.Sleep(3000);
Button btn = (Button)sender;
KaplanFTP.BatchFiles bf = new KaplanFTP.BatchFiles();
KaplanFTP.Transmit transmit = new KaplanFTP.Transmit();
//label text change here
if (btn.ID == PutFTPButton.ID)
{
//bf.ReadyFilesForTransmission();
DirectoryInfo dir = new DirectoryInfo(#"C:\Kaplan");
FileInfo[] BatchFiles = bf.GetBatchFiles(dir);
bool result = transmit.UploadBatchFilesToFTP(BatchFiles);
//label text change here
if (!result)
{
ErrorLabel.Text += KaplanFTP.errorMsg;
return;
}
bf.InsertBatchDataIntoDatabase("CTL");
bf.InsertBatchDataIntoDatabase("HDR");
bf.InsertBatchDataIntoDatabase("DET");
bf.InsertBatchDataIntoDatabase("NTS");
List<FileInfo> allfiles = BatchFiles.ToList<FileInfo>();
allfiles.AddRange(dir.GetFiles("*.txt"));
bf.MoveFiles(allfiles);
//label text change here
foreach (string order in bf.OrdersSent)
{
OrdersSentDiv.Controls.Add(new LiteralControl(order + "<br />"));
}
//lblWait.Visible = false;
OrdersSentDiv.Visible = true;
OrdersInfoDiv.Visible = false;
SuccessLabel.Visible = true;
NoBatchesToProcessLbl.Visible = true;
BatchesToProcessLbl.Visible = false;
PutFTPButton.Enabled = false;
BatchesCreatedLbl.Text = int.Parse(NextBatchNum).ToString();
Thread.Sleep(20000);
if (KaplanFTP.errorMsg.Length != 0)
{
ErrorLabel.Visible = true;
SuccessLabel.Visible = false;
ErrorLabel.Text = KaplanFTP.errorMsg;
}
}
}
I think you can use an Ajax UpdateProgress control, check Progress Bar on File Upload ASP.NET.
EDIT: Another one Displaying Progress Bar For Long Running Processes using ASP.NET AJAX.
Application.DoEvents() is not available in an ASP.NET application, nor is it's use acceptable in a standard WinForms application with the advent of multicore processors and the .NET threading library.
A web application requires communication to/from a server. Therefore simply updating the text of a label does nothing unless you are sending that back to the client. In your case you would need an event which was signaled by this line (because it is a batch upload):
transmit.UploadBatchFilesToFTP(BatchFiles);
The event would update the value you want to display. You would then need some AJAX code (or an ASP.NET update panel around a ASP.NET label) on the web page in question to get and display the new value.
HTH
delegate void SetTextCallback(string text);
private void SetText(string text)
{
if (this.label1.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
this.Invoke(d, new object[] { text });
}
else this.label1.Text = text;
}
void SomeMethod()
{
SetText(yourVariable.ToString());
}
if i understand you correctly this should work.