How can I do to access an element from another thread? In the case, I have a richtextbox in the Main Thread (GUI), and I'm running a method on a secondary thread. I want to access the richeditbox through the secondary thread
private void Log(string input, Label lbl)
{
lbl.Invoke(new Action(()=>
{
lbl.Text = "Status: " + input;
Thread.Sleep(50);
}));
}
void Run()
{
foreach (string line in richTextBox1.Lines)
{
Log(line, label1);
Thread.Sleep(500);
}
}
private void button1_Click(object sender, EventArgs e)
{
ThreadStart th = new ThreadStart(() => Run());
Thread th2 = new Thread(th);
th2.Start();
//th2.Join();
}
The following error is shown:
Invalid thread operation: control 'richTextBox1' accessed from a
thread that is not the one in which it was created.
You're already doing this. Your Log method shows the correct thing to do -- use Invoke to run some code on the UI thread. In this case, you could do something like:
void Run()
{
var getLines = new Func<object>(() => richTextBox1.Lines);
var lines = (string[]) richTextBox1.Invoke(getLines);
foreach (var line in lines)
{
Log(line, label1);
Thread.Sleep(500);
}
}
However, this really isn't necessary. It looks like you really want to read the Lines property once when your button is clicked and just pass it to the background thread.
void Run(string[] lines)
{
foreach (var line in lines)
{
Log(line, label1);
Thread.Sleep(500);
}
}
private void button1_Click(object sender, EventArgs e)
{
var lines = richTextBox1.Lines;
var th = new ThreadStart(() => Run(lines));
var th2 = new Thread(th);
th2.Start();
}
Here's another version...not that you shouldn't be sleeping in the Log() method as that is running in the UI thread!
private void button1_Click(object sender, EventArgs e)
{
ThreadStart th = new ThreadStart(() => Run());
Thread th2 = new Thread(th);
th2.Start();
}
void Run()
{
string[] lines = (string[])richTextBox1.Invoke(new Func<string[]>(() => richTextBox1.Lines));
foreach (string line in lines)
{
Log(line, label1);
Thread.Sleep(500);
}
}
private void Log(string input, Label lbl)
{
lbl.Invoke(new Action(() =>
{
lbl.Text = "Status: " + input;
}));
}
Related
No work await Task.Run():
private async void button2_Click(object sender, EventArgs e)
{
await Task.Run(() => {
monitor_r(label1);
});
}
protected async Task monitor_r(Label L1)
{
MessageBox.Show(L1.Name);
L1.ForeColor = Color.Blue;
L1.Text = "test";
}
These commands
MessageBox.Show(L1.Name);
and
L1.ForeColor = Color.Blue;
works fine but
L1.Text = "test";
does not work.
Can you help, why do not change a Label Text?
Try Control.Invoke: we should run Winform UI in the main thread only
protected async Task monitor_r(Label L1)
{
Action action = () =>
{
MessageBox.Show(L1.Name);
L1.ForeColor = Color.Blue;
L1.Text = "test";
};
if (L1.InvokeRequired)
L1.Invoke(action); // When in different thread
else
action(); // When in the main thread
}
If you're on debug mode, take a look at the output window. It should shows exception message something like this:
System.InvalidOperationException' in System.Windows.Forms.dll.
That because label1 accessed from a thread other than the thread it was created on. And it will causing invalid cross-thread operation.
You can solve this by using Control.Invoke as Dmitry Bychenko already mentioned. Here is simple extension to make thread-safe calls to Winforms Control.
public static void TryInvoke(this Control control, Action<Control> action)
{
if (control.InvokeRequired) control.Invoke(new Action(() => action(control)));
else action(control);
}
Sample usage
label1.TryInvoke(x => x.Text = "test");
label1.TryInvoke(x => x.ForeColor = Color.Blue);
Or
this.TryInvoke(x =>
{
label1.Text = "test";
label1.ForeColor = Color.Blue;
});
Secondly, since you don't await anything at monitor_r, i'd recommend to use void instead of async Task.
Even if you're await something at monitor_r you don't need
await Task.Run(() => {
monitor_r(label1);
});
..because monitor_r itself is a task. So just call await monitor_r(label1);
If you wish to have a separate thread, you can try this using BackgroundWorker. You can implement the ReportProgress if you have a loop.
private void button1_Click(object sender, EventArgs e)
{
BackgroundWorker worker = new BackgroundWorker()
{
WorkerReportsProgress = true,
WorkerSupportsCancellation = true
};
worker.RunWorkerCompleted += Worker_RunWorkerCompleted;
worker.RunWorkerAsync();
}
private void Worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
MessageBox.Show(label1.Name);
label1.ForeColor = Color.Blue;
label1.Text = "test";
}
I'm working on a WPF application in Visual Studio, I need to download a large file and extract it in my code. Someone recommended that I use background workers, but now when I try to increase the value on my progress bar it doesn't work... Can anyone help?
public void InstallVersion(string version)
{
string location = File.ReadAllText(#"C:\Users\" + Environment.UserName + #"\AppData\Roaming\MidnightFallsLauncher\data\locator.txt");
location = location + #"\Versions\" + version;
if (File.Exists(location + ".zip"))
File.Delete(location + ".zip");
if (Directory.Exists(location))
{
DirectoryInfo di = new DirectoryInfo(location);
foreach (FileInfo file in di.GetFiles())
{
file.Delete();
}
foreach (DirectoryInfo dir in di.GetDirectories())
{
dir.Delete(true);
}
}
if (!myWorker.IsBusy)
{
myWorker.RunWorkerAsync();
}
}
And here is my worker code
public MainWindow()
{
InitializeComponent();
myWorker.DoWork += new DoWorkEventHandler(myWorker_DoWork);
myWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(myWorker_RunWorkerCompleted);
myWorker.ProgressChanged += new ProgressChangedEventHandler(myWorker_ProgressChanged);
myWorker.WorkerReportsProgress = true;
myWorker.WorkerSupportsCancellation = true;
}
protected void myWorker_DoWork(object sender, DoWorkEventArgs e)
{
string location = File.ReadAllText(#"C:\Users\" + Environment.UserName + #"\AppData\Roaming\MidnightFallsLauncher\data\locator.txt");
location = location + #"\Versions\" + Version;
WebClient Client = new WebClient();
string url = "";
string content = "";
string downloadlink = "";
List<string> availibleVersions = new List<string>();
List<string> versionDownload = new List<string>();
url = "https://midnightfalls.glitch.me/versions.html";
content = Client.DownloadString(url);
foreach (string line in content.Split(new string[] { "<br>", "<br />" }, StringSplitOptions.None))
{
if (line.Contains("0"))
{
availibleVersions.Add(line);
}
}
url = "https://midnightfalls.glitch.me/versionslink.html";
content = Client.DownloadString(url);
foreach (string line in content.Split(new string[] { "<br>", "<br />" }, StringSplitOptions.None))
{
if (line.Contains("https"))
{
versionDownload.Add(line);
}
}
for (var i = 0; i < availibleVersions.Count; i++)
{
if (availibleVersions[i] == Version)
{
downloadlink = versionDownload[i];
}
}
Client.DownloadFile(downloadlink, location + ".zip");
ZipFile.ExtractToDirectory(location + ".zip", location);
File.Delete(location + ".zip");
RunGame(Version);
}
protected void myWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
}
protected void myWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
this.Dispatcher.Invoke(() =>
{
progress.Value += 10;
});
}
Also, while my worker is running, the UI freezes... I'm pretty sure that's not meant to happen.
EDIT:
The UI is now updating but the progress bar still doesnt work...
It looks like the problem is that the main thread is constantly working while the background worker is doing its work:
while (this.myWorker.IsBusy)
{
this.Dispatcher.Invoke(() =>
{
progress.Value += 10;
});
}
means that your main thread is constantly doing stuff while the background job is working, which is why the UI doesn't update.
You need to move the progress update to the background worker (where you could also set a value that actually makes some sense, e.g. to indicate how many of the 'availableVersion's you have downloaded).
Hope that makes sense.
EDIT:
Suppose we'll put all the code directly in the view, so assume we have a progress bar named 'progressBar' and a button named 'btnStart' (which kicks of the backgroundworker).
Here's the codebehind:
private BackgroundWorker worker;
public MainWindow()
{
InitializeComponent();
this.worker = new BackgroundWorker();
this.worker.DoWork += new DoWorkEventHandler(myWorker_DoWork);
this.worker.RunWorkerCompleted += new
RunWorkerCompletedEventHandler(myWorker_RunWorkerCompleted);
this.worker.ProgressChanged += new
ProgressChangedEventHandler(myWorker_ProgressChanged);
this.worker.WorkerReportsProgress = true;
this.worker.WorkerSupportsCancellation = true;
}
private void myWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
this.progressBar.Value = e.ProgressPercentage;
}
private void myWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
// Whatever you need to do when finished here (alert, update a label, etc.)
}
private void myWorker_DoWork(object sender, DoWorkEventArgs e)
{
// Just loop and report new progress. Sleep a little in between each
// progress update so that it isn't over before we have a chance to see it.
for(int i=0;i<100;i++)
{
Thread.Sleep(200);
this.worker.ReportProgress(i);
}
}
private void btnStart_Click(object sender, RoutedEventArgs e)
{
this.worker.RunWorkerAsync();
}
What happens is that the background worker fires an event notifying that progress has changed.
The main thread has a handle on that event, and updates the progress bar.
Since it's a background worker you don't need to use Dispatcher.Invoke - this is already taken care of.
Hope the example clarifies things for you.
I'm pretty sure you're blocking right here:
while (this.myWorker.IsBusy)
{
this.Dispatcher.Invoke(() =>
{
progress.Value += 10;
});
}
You should be calling ReportProgress on your BackgroundWorker instance within your myWorker_DoWork method.
Also, if you're using .NET 4.5 or later, you can dump the BackgroundWorker entirely and rewrite this code using the async/await pattern.
I'm trying to open new windows form with thread and task, but this code open new windows, but do not show buttons, textfield, etc on it (form is loading)
private void newFomrm_Click(object sender, EventArgs e)
{
NewForm a = new NewForm(param); // my Form
Action showMethod = () => { a.Show(); };
Task t1 = new Task(showMethod);
Thread t = new Thread(new ThreadStart(t1.Start));
t.Start();
}
private void button1_Click(object sender, EventArgs e)
{
NewForm a = new NewForm(); // my Form
Action showMethod = () => {
Invoke(new Action(() => a.Show()));
};
Task t1 = new Task(showMethod);
Thread t = new Thread(new ThreadStart(t1.Start));
t.Start();
}
try this...you have to put the UI operation on the main thread
private void button1_Click(object sender, EventArgs e)
{
button1.Enabled = false;
string IDs = ID.Text;
string[] eachIDs = Regex.Split(IDs, "\n");
foreach (var eachID in eachIDs)
{
getContent(eachID);
titleBox.Text = "Done";
}
}
private void getContent(string value)
{
label1.Text = value;
Thread.Sleep(5000);
}
I will give 4 id's as Input say "IDNUMBER01, IDNUMBER02, IDNUMBER03, IDNUMBER04" each in a new line in Rich Text Box.
The code splits them successfully. I want to show the Value of the ID being used in the current loop in a Label Text.
Problem with my code is it shows only the last ID which goes through the loop.
Probably your UI freezing and you can't see the changes.Try this, use async/await feature:
private async void button1_Click(object sender, EventArgs e)
{
button1.Enabled = false;
string IDs = ID.Text;
string[] eachIDs = Regex.Split(IDs, "\n");
foreach (var eachID in eachIDs)
{
await getContent(eachID);
titleBox.Text = "Done";
}
}
private async Task getContent(string value)
{
label1.Text = value;
await Task.Delay(5000);
}
This is because the UI is only Updated after the execution of this code, since they are executing in the same thread. You will need to open a thread, run this code, and call the dispatcher (or the Control.BeginInvoke if this app is Winforms) to update the UI.
EDIT
Try this:
private void button1_Click(object sender, EventArgs e)
{
button1.Enabled = false;
string IDs = ID.Text;
new System.Threading.Thread(() =>
{
string[] eachIDs = Regex.Split(IDs, "\n");
foreach (var eachID in eachIDs)
{
getContent(eachID);
titleBox.BeginInvoke((Action) delegate { titleBox.Text = "Done"; });
}
}).Start();
}
private void getContent(string value)
{
label1.BeginInvoke((Action) delegate { label1.Text = value; });
Thread.Sleep(5000);
}
In your example, you'd be better using a timer to display your value text. You're only seeing the last ID because the loop is executing very quickly, and using Thread.Sleep within the foreach isn't going to fly.
You could use Application.DoEvents() before the Thread.Sleep, but a timer is still your better option ... imho.
I have been trying to implement a BackgroundWorker into my application, and so far, it has not gone well. On a new thread, I want to open up a new Form that will have a progressbar and a label to report progress, however, this is not working well. When I call ShowDialog, the application does not respond any more. Is this because my code is running from my Form1, and I am showing WorkingForm? Also, can this be implemented cleaner?
private void button14_Click(object sender, EventArgs e)
{
List<object> param = new List<object>();
object[] objectparams = new object[1];
objectparams[0] = null;
Opera opera = new Opera();
System.Reflection.MethodInfo clearOpera = opera.GetType().GetMethod("ClearOpera");
param.Add(clearOpera);
param.Add(opera);
param.Add(objectparams);
backgroundWorker1.RunWorkerAsync(param);
}
private void button2_Click_1(object sender, EventArgs e)
{
Browser.cancelPending = true;
}
private delegate void getnewform();
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
mainForm main = new mainForm();
TestURLGUI4.Form1 form = (TestURLGUI4.Form1)Application.OpenForms[0];
var variab = (bool)form.Invoke(new getnewform(main.AskForConfirmation));
List<object> param = e.Argument as List<object>;
List<object> result = new List<object>();
var method = param[0] as MethodInfo;
object[] parameters = param[2] as object[];
if (parameters[0] == null)
{
result.Add(method.Invoke(param[1], null));
result.Add(false);
}
else
{
result.Add(method.Invoke(param[1], parameters));
if (parameters.Contains(true))
result.Add(true);
}
int progress = (100 * Browser.progressValue) / Browser.progressMax;
backgroundWorker1.ReportProgress(progress);
// If the BackgroundWorker.CancellationPending property is true, cancel
if (backgroundWorker1.CancellationPending)
{
Console.WriteLine("Cancelled");
Browser.cancelPending = true;
}
e.Result = result;
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
TestURLGUI4.WorkingForm form = (TestURLGUI4.WorkingForm)Application.OpenForms[1];
form.progressBar1.Value = e.ProgressPercentage;
form.label1.Text = Browser.progressValue + "/" + Browser.progressMax;
Application.DoEvents();
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
List<object> param = e.Result as List<object>;
if (e.Cancelled == false && param.Contains(true))
{
Display.DisplayURLs(param[0] as SortableBindingList<URL>);
TestURLGUI4.WorkingForm form = (TestURLGUI4.WorkingForm)Application.OpenForms[1];
MessageBox.Show("Done");
}
else if (e.Cancelled == false && param.Contains(false))
{
TestURLGUI4.WorkingForm form = (TestURLGUI4.WorkingForm)Application.OpenForms[1];
MessageBox.Show("Done");
}
}
public class mainForm
{
public void AskForConfirmation()
{
TestURLGUI4.Form1 form = (TestURLGUI4.Form1)Application.OpenForms[0];
var workingForm = new TestURLGUI4.WorkingForm();
workingForm.ShowDialog(form);
workingForm.DialogResult = DialogResult.None;
}
}
Edit:
Ok, I have updated my code according to the suggestions, and now, this produces a stackoverflowexception in System.Windows.Forms.dll:
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
mainForm main = new mainForm();
TestURLGUI4.Form1 form = (TestURLGUI4.Form1)Application.OpenForms[0];
List<object> param = e.Argument as List<object>;
List<object> result = new List<object>();
var method = param[0] as MethodInfo;
object[] parameters = param[2] as object[];
if (parameters[0] == null)
{
result.Add(method.Invoke(param[1], null));
result.Add(false);
}
else
{
result.Add(method.Invoke(param[1], parameters));
if (parameters.Contains(true))
result.Add(true);
}
int progress = (100 * Browser.progressValue) / Browser.progressMax;
backgroundWorker1.ReportProgress(progress);
// If the BackgroundWorker.CancellationPending property is true, cancel
if (backgroundWorker1.CancellationPending)
{
Console.WriteLine("Cancelled");
Browser.cancelPending = true;
}
e.Result = result;
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
TestURLGUI4.Form1 form1 = (TestURLGUI4.Form1)Application.OpenForms[0];
if (Application.OpenForms.Count >= 2)
{
TestURLGUI4.WorkingForm form2 = (TestURLGUI4.WorkingForm)Application.OpenForms[1];
form2.progressBar1.Value = e.ProgressPercentage;
form2.label1.Text = Browser.progressValue + "/" + Browser.progressMax;
Application.DoEvents();
}
else if(Application.OpenForms.Count == 1)
{
var workingForm = new TestURLGUI4.WorkingForm();
workingForm.ShowDialog(form1);
}
}
The purpose of a BackgroundWorker is to invoke code on another thread (not the UI thread). By calling Invoke in the DoWork method, you're completely circumventing the purpose of BackgroundWorker. Do all your UI work before you start the worker. If you need to interact with the user while the worker is working, do it in the ProgressChanged handler--it runs on the UI thread and you don't need to use Invoke in ProgressChanged.
By invoking UI work in DoWork, you run the risk of a deadlock, which will hang your program
you cant run UI on other threads. Has to be on the main thread.
Instantiate the UI before you start the new thread. In the new thread use cross thread invoke methods on the controls you want to work with. Look here for example http://msdn.microsoft.com/en-us/library/ms171728.aspx