I'm trying to get a simple label value to change from another thread, and already tried 3 different threading mechanisms (Tasks, Thread, Background worker) and am now at a loss why the control won't update.
I have a method in an unrelated class like this:
public static void SetOverlayText(string text, bool fade = false)
{
Thread myThread = new Thread(FadeOverlayText);
OverlayForm.SetLabelText(text);
if (fade)
{
myThread.Start();
}
}
and
private static void FadeOverlayText()
{
OverlayForm.ClearLabelText();
}
My form is a regular windows form and has that method:
public void ClearLabelText()
{
this.Invoke((MethodInvoker)delegate
{
StatusText.Text = "Something should happen"
StatusText.Refresh();
});
}
The method appears to be getting called, but nothing happens.
You should not need Refresh.
This should work:
public void ClearLabelText()
{
if (StatusText.InvokeRequired)
{
this.Invoke((MethodInvoker)delegate
{
StatusText.Text = "Something should happen";
});
}
else
{
StatusText.Text = "Something should happen";
}
}
Are you shure, you use the correct control and at no other point the string is changed, so that it seems not to work? Please check every thing.
Also be sure, that you only call ClearLabelText once in your second thread, becuase after ClearLabelText is finished, the thread is not alive anymore.
This will update your text every second, as long as the application runs:
private static void FadeOverlayText()
{
var uiThread = <<Your UI Thread>>;
while(uiThread.IsAlive)
{
OverlayForm.ClearLabelText();
Thread.Sleep(1000);
}
}
EDIT:
here is a simple example i've made and it works. Additionaly to your StatusText label, I've added button1, which change the text too.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading;
using System.Windows.Forms;
namespace ThreadTest2
{
public partial class Form1 : Form
{
Thread mainThread = null;
public Form1()
{
InitializeComponent();
mainThread = Thread.CurrentThread;
Thread myThread = new Thread(FadeOverlayText);
myThread.Start();
}
private void FadeOverlayText()
{
while (mainThread.IsAlive)
{
ClearLabelText();
Thread.Sleep(1000);
}
}
public void ClearLabelText()
{
if (StatusText.InvokeRequired)
{
this.Invoke((MethodInvoker)delegate
{
StatusText.Text = "Something should happen";
});
}
else
{
StatusText.Text = "Something should happen";
}
}
private void button1_Click(object sender, EventArgs e)
{
StatusText.Text = "It works!";
}
}
}
One way to make this work is to use a timer that does
StatusText.Text= yourstring;
Every n milliseconds, and make your thread update the 'yourstring' variable to whatever you want.
Related
I've gotten this type of thing working in the past with a BackgroundWorker, but I want to use the new async/await approach of .NET 4.5. I may be barking up the wrong tree. Please advise.
Goal: Create a component that will do some long-running work and show a modal form with a progress bar as it's doing the work. The component will get the handle to a window to block interaction while it's executing the long-running work.
Status: See the code below. I thought I was doing well until I tried interacting with the windows. If I leave things alone (i.e. don't touch!), everything runs "perfectly", but if I do so much as click on either window the program hangs after the long-running work ends. Actual interactions (dragging) are ignored as though the UI thread is blocked.
Questions: Can my code be fixed fairly easily? If so, how? Or, should I be using a different approach (e.g. BackgroundWorker)?
Code (Form1 is a standard form with a ProgressBar and a public method, UpdateProgress, that sets the ProgressBar's Value):
using System;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Starting..");
var mgr = new Manager();
mgr.GoAsync();
Console.WriteLine("..Ended");
Console.ReadKey();
}
}
class Manager
{
private static Form1 _progressForm;
public async void GoAsync()
{
var owner = new Win32Window(Process.GetCurrentProcess().MainWindowHandle);
_progressForm = new Form1();
_progressForm.Show(owner);
await Go();
_progressForm.Hide();
}
private async Task<bool> Go()
{
var job = new LongJob();
job.OnProgress += job_OnProgress;
job.Spin();
return true;
}
void job_OnProgress(int percent)
{
_progressForm.UpdateProgress(percent);
}
}
class LongJob
{
public event Progressed OnProgress;
public delegate void Progressed(int percent);
public void Spin()
{
for (var i = 1; i <= 100; i++)
{
Thread.Sleep(25);
if (OnProgress != null)
{
OnProgress(i);
}
}
}
}
class Win32Window : IWin32Window
{
private readonly IntPtr _hwnd;
public Win32Window(IntPtr handle)
{
_hwnd = handle;
}
public IntPtr Handle
{
get
{
return _hwnd;
}
}
}
}
The async and await keywords do not mean "run on a background thread." I have an async/await intro on my blog that describes what they do mean. You must explicitly place CPU-bound operations on a background thread, e.g., Task.Run.
Also, the Task-based Asynchronous Pattern documentation describes the common approaches with async code, e.g., progress reporting.
class Manager
{
private static Form1 _progressForm;
public async Task GoAsync()
{
var owner = new Win32Window(Process.GetCurrentProcess().MainWindowHandle);
_progressForm = new Form1();
_progressForm.Show(owner);
var progress = new Progress<int>(value => _progressForm.UpdateProgress(value));
await Go(progress);
_progressForm.Hide();
}
private Task<bool> Go(IProgress<int> progress)
{
return Task.Run(() =>
{
var job = new LongJob();
job.Spin(progress);
return true;
});
}
}
class LongJob
{
public void Spin(IProgress<int> progress)
{
for (var i = 1; i <= 100; i++)
{
Thread.Sleep(25);
if (progress != null)
{
progress.Report(i);
}
}
}
}
Note that the Progress<T> type properly handles thread marshaling, so there's no need for marshaling within Form1.UpdateProgress.
#StephenCleary's answer is correct. Though, I had to make a little modification to his answer to get the behavior what I think OP wants.
public void GoAsync() //no longer async as it blocks on Appication.Run
{
var owner = new Win32Window(Process.GetCurrentProcess().MainWindowHandle);
_progressForm = new Form1();
var progress = new Progress<int>(value => _progressForm.UpdateProgress(value));
_progressForm.Activated += async (sender, args) =>
{
await Go(progress);
_progressForm.Close();
};
Application.Run(_progressForm);
}
private async void button1_Click(object sender, EventArgs e)
{
IProgress<int> progress = new Progress<int>(value => { progressBar1.Value = value; });
await Task.Run(() =>
{
for (int i = 0; i <= 100; i++)
progress.Report(i);
});
}
Correct me if I'm wrong, but this seems to be the easiest way to update a progress bar.
I am working on converting a console application into a windowed format and as someone who knows little about it but has had experience with a similar application already in window format in the past I figured it wouldn't be too hard.
So I created a form and added a textbox to it just to get the logging information to start with.
This console app used to run in a single thread, I have since added a second thread to allow the form to run side by side with the console for testing. (it runs fine in a single thread strangely now too).
This is the code I am using to write text to the form except that I am not getting ANYTHING at all on the form.
static Form1 f = new Form1();
delegate void SetTextCallback(string s);
private void SetText(string text)
{
// InvokeRequired required compares the thread ID of the
// calling thread to the thread ID of the creating thread.
// If these threads are different, it returns true.
if (f.textBox1.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
f.textBox1.Invoke(d, new object[] { text });
}
else
{
f.textBox1.AppendText(text);
}
}
I can confirm that there is text entering the "text" variable but it is not getting to the form.
Any help would be appreciated.
This is the full file:
using System;
using System.Windows.Forms;
using Chraft.Properties;
using System.IO;
using Chraft.Plugins.Events.Args;
using Chraft.Plugins.Events;
namespace Chraft
{
public class Logger
{
private StreamWriter WriteLog;
private Server Server;
internal Logger(Server server, string file)
{
Server = server;
try
{
WriteLog = new StreamWriter(file, true);
WriteLog.AutoFlush = true;
}
catch
{
WriteLog = null;
}
}
~Logger()
{
try
{
WriteLog.Close();
}
catch
{
}
}
public void Log(LogLevel level, string format, params object[] arguments)
{
Log(level, string.Format(format, arguments));
}
public void Log(LogLevel level, string message)
{
//Event
LoggerEventArgs e = new LoggerEventArgs(this, level, message);
Server.PluginManager.CallEvent(Event.LOGGER_LOG, e);
if (e.EventCanceled) return;
level = e.LogLevel;
message = e.LogMessage;
//End Event
LogToConsole(level, message);
LogToForm(level, message);
LogToFile(level, message);
}
private void LogToConsole(LogLevel level, string message)
{
if ((int)level >= Settings.Default.LogConsoleLevel)
{
Console.WriteLine(Settings.Default.LogConsoleFormat, DateTime.Now, level.ToString().ToUpper(), message);
}
}
static Form1 f = new Form1();
delegate void SetTextCallback(string s);
private void SetText(string text)
{
// InvokeRequired required compares the thread ID of the
// calling thread to the thread ID of the creating thread.
// If these threads are different, it returns true.
if (f.textBox1.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
f.textBox1.Invoke(d, new object[] { text });
}
else
{
f.textBox1.AppendText(text);
}
}
private void LogToForm(LogLevel level, string message)
{
if ((int)level >= Settings.Default.LogConsoleLevel)
{
SetText(DateTime.Now + level.ToString().ToUpper() + message);
}
}
private void LogToFile(LogLevel level, string message)
{
if ((int)level >= Settings.Default.LogFileLevel && WriteLog != null)
WriteLog.WriteLine(Settings.Default.LogFileFormat, DateTime.Now, level.ToString().ToUpper(), message);
}
public void Log(Exception ex)
{
//Event
LoggerEventArgs e = new LoggerEventArgs(this, LogLevel.Debug, ex.ToString(), ex);
Server.PluginManager.CallEvent(Event.LOGGER_LOG, e);
if (e.EventCanceled) return;
//End Event
Log(LogLevel.Debug, ex.ToString());
}
public enum LogLevel : int
{
Trivial = -1,
Debug = 0,
Info = 1,
Warning = 2,
Caution = 3,
Notice = 4,
Error = 5,
Fatal = 6
}
}
}
The problem is that you are creating two Form objects. One that is created in your Program.cs file:
Application.Run(new Form1());
And the one you created in your logger class
Form f = new Form1();
The one passed to Application.Run is the one that the user is interacting with. It has become visible and responds to user interaction because of the Application.Run call.
The one you created on your logger class just sits there in memory. Its TextBox is happily adding the text you ask it to, but that one isn't visible anywhere.
There are many ways to handle this situation. You could gain access to the correct Form object through Application.OpenForms, but a more appropriate way to handle it would be to add an event on the logger that the form can subscribe to and it can handle updating the TextBox in response to the event.
Updated
class LoggerLogEventArgs : EventArgs
{
public LoggerLogEventArgs(string message)
{
this.message = message;
}
private string message;
public string Message { get { return message; } }
}
class Logger
{
public event EventHandler<LoggerLogEventArgs> Logged;
protected virtual void OnLogged(LoggerLogEventArgs e)
{
EventHandler<LoggerLogEventArgs> handler = Logged;
if (handler != null)
handler(this, e);
}
// I would change this method name to LogToEvent
private void LogToForm(LogLevel level, string message)
{
if ((int)level >= Settings.Default.LogConsoleLevel)
{
OnLogged(new LoggerLogEventArgs(message));
}
}
}
class Form1 : Form
{
// Subscribe to the logger only when we are ready to display text
protected override void OnHandleCreated(EventArgs e)
{
base.OnHandleCreated(e);
GetLog().Logged += new EventHandler<LoggerLogEventArgs>(logger_Logged);
}
// Unsubscribe from the logger before we are no longer ready to display text
protected override void OnHandleDestroyed(EventArgs e)
{
GetLog().Logged -= new EventHandler<LoggerLogEventArgs>(logger_Logged);
base.OnHandleDestroyed(e);
}
private void logger_Logged(object sender, LoggerLogEventArgs e)
{
if (InvokeRequired)
BeginInvoke(new EventHandler<LoggerLogEventArgs>(logger_Logged), e);
else
textBox1.AppendText(e.Message);
}
}
hello i try this it works ( I make a console application and I add a windows form)
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security.Permissions;
using System.Windows.Forms;
namespace ConsoleApplication6
{
class Program
{
delegate void SetTextCallback(string s);
static Form1 f;
static void Main(string[] args)
{
f = new Form1();
f.Show();
SetText("test");
Console.ReadLine();
}
private static void SetText(string text)
{
// InvokeRequired required compares the thread ID of the
// calling thread to the thread ID of the creating thread.
// If these threads are different, it returns true.
if (f.textBox1.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
f.textBox1.Invoke(d, new object[] { text });
}
else
{
f.textBox1.AppendText(text);
}
}
}
}
Delay.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
namespace LearnThread
{
class Delay
{
public int Convert()
{
int ErrorCode = 1;
//something
//takes long time. about 9 hours.
return ErrorCode;
}
}
}
Form1.cs
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;
namespace LearnThread
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void btnStart_Click(object sender, EventArgs e)
{
Delay delay = new Delay();
Thread t = new Thread(delay.Convert);
//something
MessageBox.Show("Success");
}
}
}
Delay delay = new Delay(); is error here as it is expecting return value. I want the return value as it is contains errorcode. How can I do that? Background worker is better than Thread? Please help. (I should not lose control on the form when delay.Convert() is running.)
As mentioned by Juergen, you can make ErrorCode a class member and then access it once the thread has completed execution. This would require you to create a new instance of the Delay class if you are trying to run multiple Convert in parallel.
You can also use a delegate to get the return value to a variable in the btnStart_Click function as follows:
private void button1_Click(object sender, EventArgs e)
{
Delay delay = new Delay();
int delayResult = 0;
Thread t = new Thread(delegate() { delayResult = delay.Convert(); });
t.Start();
while (t.IsAlive)
{
System.Threading.Thread.Sleep(500);
}
MessageBox.Show(delayResult.ToString());
}
If you plan to run Convert in parallel here, you would have to create as many local variable as required or handle it someother way.
Make the ErrorCode a class member. This way you can get it afterwards.
class Delay
{
public int ErrorCode { get; private set; }
public void Convert()
{
ErrorCode = 1;
...
}
}
private void btnStart_Click(object sender, EventArgs e)
{
Delay delay = new Delay();
Thread t = new Thread(delay.Convert);
//something
int error = delay.ErrorCode;
MessageBox.Show("Success");
}
This program is writing numbers from 1 to 5000 in thread, but main form freezes anyway.
Where is an error? Thanks in advance.
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.Net;
using System.IO;
using System.Threading;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
int how, current;
bool job;
Object lockobj = new Object();
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
MessageBox.Show("Started!");
how = 5000;
current = 0;
job = true;
Thread worker = new Thread(Go);
worker.Name = "1";
worker.Start();
}
private void Go()
{
while (job)
{
if (current < how)
{
lock (lockobj)
{
current++;
}
log(string.Format("Thread #{0}: {1}", Thread.CurrentThread.Name, current));
}
else
{
job = false;
}
}
}
private void log(string text)
{
Action A = new Action(() =>
{
richTextBox1.AppendText(text + System.Environment.NewLine);
});
if (richTextBox1.InvokeRequired)
this.BeginInvoke(A);
else A();
}
}
}
Because most of your work will be spent in
if (richTextBox1.InvokeRequired)
this.BeginInvoke(A);
and while you invoke the form it is locked.
Do some real work, like Thread.Sleep(1000); :-) , instead of current++; and your form will be response between the updates.
It freezes because you are rendering on the textbox very quickly and the GUI doesn't have time to keep in sync. Remember that this rendering happens on the main GUI thread and by calling BeginInvoke to update the textbox so rapidly actually consumes all the resources of this main GUI thread. Try lowering the frequency at which you are logging to avoid this behavior.
How do I bind a ProgressBar to a property of a class updated in another thread?
The following code example shows my first naive attempt. It doesn't work because I get runtime errors about cross thread communication. I think I need to use Invoke in some way, but I'm not sure how to do it with the Binding class.
using System;
using System.Drawing;
using System.Windows.Forms;
using System.ComponentModel;
using System.Threading;
class ProgressForm : Form
{
private ProgressBar pbProgress;
public ProgressForm(ref LongOp lo)
{
Binding b = new Binding("Value", lo, "Progress");
pbProgress = new ProgressBar();
pbProgress.DataBindings.Add(b);
this.Controls.Add(pbProgress);
}
}
class Program : Form
{
private Button btnStart;
private LongOp lo;
public Program()
{
lo = new LongOp();
btnStart = new Button();
btnStart.Text = "Start long operation";
btnStart.Click += new EventHandler(btnStart_Click);
this.Controls.Add(btnStart);
}
private void btnStart_Click(object sender, EventArgs e)
{
ProgressForm pf = new ProgressForm(ref lo);
lo.DoLongOp();
pf.ShowDialog();
}
[STAThread]
public static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Program());
}
}
class LongOp : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private int progress;
public void DoLongOp()
{
Thread thread = new Thread(new ThreadStart(this.run));
thread.Start();
}
public void run()
{
for (int i = 0; i < 10; ++i)
{
Thread.Sleep(1000);
Progress++;
}
}
public int Progress
{
get
{
return progress;
}
set
{
progress = value;
NotifyPropertyChanged("Progress");
}
}
private void NotifyPropertyChanged(String field)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(field));
}
}
}
So how do I bind a ProgressBar to a value updated in another thread?
Thanks in advance
EDIT: I've switched to using the ThreadedBinding implementation Mr. Gravell wrote and linked to. I'm still getting the cross thread exception though. Pressing "Break" in the exception dialog highlights the PropertyChanged(this, new PropertyChangedEventArgs(field)); line as the line causing the exception.
What more do I need to change?
EDIT: Looks like Mr. Gravell's post has been removed. The ThreadedBinding implementation I mentioned can be found at the end of this thread: http://groups.google.com/group/microsoft.public.dotnet.languages.csharp/browse_thread/thread/69d671cd57a2c7ab/2f078656d6f1ee1f?pli=1
I've switched back to plain old Binding in the example for easier compilation by others.
Unfortunately I think the cross-threading issues will make data-binding proper a bit too clumsy to use here, and probably more complexity than you need in any case -- the data only needs to be plumbed one way.
You could just replace the binding with an event handler like this:
private void ProgressPropertyChangedHandler(object sender,
PropertyChangedEventArgs args)
{
// fetch property on event handler thread, stash copy in lambda closure
var progress = LongOp.Progress;
// now update the UI
pbProgress.Invoke(new Action(() => pbProgress.Value = progress));
}