Cross-thread operation not valid: Control '' accessed from a thread other than the thread it was created on.
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Hi there, I am creating my first multi threading app. And I now I'm stuck on here. Here's my Code:
public partial class FrmMain : Form { Thread threadVBNums, threadCNum; private void StartProcess() { this.threadVBNums = new Thread(new ThreadStart(this.AddVbNums)); this.threadVBNums.Start(); this.threadCNums = new Thread(new ThreadStart(this.AddCNums)); this.threadCNums.Start(); } private void AddVbNums() { for(int i = 0; i < 20, i++) { this.vbText.Text += ("Main thread: {0}\n", i); } } private void AddCNums() { for(int i = 0; i < 20, i++) { this.cText.Text += ("Main thread: {0}\n", i); } } }And this is written in Windows Application. So the other code is same as normal CS app. code. Now this gives me an error sayingCross-thread operation not valid: Control '' accessed from a thread other than the thread it was created on.
I know that .NET do not allow me access controls on form. But I don't know how to solve this??!! Can someone tell me what is happening wrong and how to solve it??
- Stop thinking in terms of limitations and start thinking in terms of possibilities -
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Hi there, I am creating my first multi threading app. And I now I'm stuck on here. Here's my Code:
public partial class FrmMain : Form { Thread threadVBNums, threadCNum; private void StartProcess() { this.threadVBNums = new Thread(new ThreadStart(this.AddVbNums)); this.threadVBNums.Start(); this.threadCNums = new Thread(new ThreadStart(this.AddCNums)); this.threadCNums.Start(); } private void AddVbNums() { for(int i = 0; i < 20, i++) { this.vbText.Text += ("Main thread: {0}\n", i); } } private void AddCNums() { for(int i = 0; i < 20, i++) { this.cText.Text += ("Main thread: {0}\n", i); } } }And this is written in Windows Application. So the other code is same as normal CS app. code. Now this gives me an error sayingCross-thread operation not valid: Control '' accessed from a thread other than the thread it was created on.
I know that .NET do not allow me access controls on form. But I don't know how to solve this??!! Can someone tell me what is happening wrong and how to solve it??
- Stop thinking in terms of limitations and start thinking in terms of possibilities -
To avoid this problem, I would suggest you use a BackgroundWorker. This component will handle much of the threading for you and allow you a way modify controls on the form. It has a few very helpful methods...RunWorkerAsync() , ReportProgress(), and WorkDone(). You can call the ReportProgress method within your for loop like
private void StartProcess() { this.bgWorker.RunWorkerAsync(); } private void bgWorker_DoWork() { AddCNums(); } private void AddCNums() { for(int i = 0; i < 20, i++) { this.bgWorker.ReportProgress(0, i)} } } private void bgWorker_ReportProgress(object sender, ProgressChangedEventArgs e) { if(e.ProgressPercentage == 0) { int i = (int)e.UserState; this.cText.Text += ("Main thread: {0}\n", i); } }It's very clean. -
Hi there, I am creating my first multi threading app. And I now I'm stuck on here. Here's my Code:
public partial class FrmMain : Form { Thread threadVBNums, threadCNum; private void StartProcess() { this.threadVBNums = new Thread(new ThreadStart(this.AddVbNums)); this.threadVBNums.Start(); this.threadCNums = new Thread(new ThreadStart(this.AddCNums)); this.threadCNums.Start(); } private void AddVbNums() { for(int i = 0; i < 20, i++) { this.vbText.Text += ("Main thread: {0}\n", i); } } private void AddCNums() { for(int i = 0; i < 20, i++) { this.cText.Text += ("Main thread: {0}\n", i); } } }And this is written in Windows Application. So the other code is same as normal CS app. code. Now this gives me an error sayingCross-thread operation not valid: Control '' accessed from a thread other than the thread it was created on.
I know that .NET do not allow me access controls on form. But I don't know how to solve this??!! Can someone tell me what is happening wrong and how to solve it??
- Stop thinking in terms of limitations and start thinking in terms of possibilities -
You'll have to add a Method to handle it that looks something like this...
private delegate void TextBoxUpdater(TextBox t, String s); private void UpdateTextBox(TextBox t, String s){ if(t.InvokeRequired) { t.Invoke(new TextBoxUpdater(UpdateTextBox), Object[]{t, s})); } else { t.Text = s; } }
Call this from your thread routine in place of manually setting the control text. The above code may not work, I didn't compile it, but you get the idea. You have to check "InvokeRequired" on a control that you want to cross thread, and call the updating method on the UI thread using a delegate. Scott"Run for your life from any man who tells you that money is evil. That sentence is the leper's bell of an approaching looter." --Ayn Rand
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Hi there, I am creating my first multi threading app. And I now I'm stuck on here. Here's my Code:
public partial class FrmMain : Form { Thread threadVBNums, threadCNum; private void StartProcess() { this.threadVBNums = new Thread(new ThreadStart(this.AddVbNums)); this.threadVBNums.Start(); this.threadCNums = new Thread(new ThreadStart(this.AddCNums)); this.threadCNums.Start(); } private void AddVbNums() { for(int i = 0; i < 20, i++) { this.vbText.Text += ("Main thread: {0}\n", i); } } private void AddCNums() { for(int i = 0; i < 20, i++) { this.cText.Text += ("Main thread: {0}\n", i); } } }And this is written in Windows Application. So the other code is same as normal CS app. code. Now this gives me an error sayingCross-thread operation not valid: Control '' accessed from a thread other than the thread it was created on.
I know that .NET do not allow me access controls on form. But I don't know how to solve this??!! Can someone tell me what is happening wrong and how to solve it??
- Stop thinking in terms of limitations and start thinking in terms of possibilities -
The "Tricky" way is just like carbon_golem suggested (and this is the correct way, u need to thank golem :):) ) the simple way and not recommended is override this by only changing the CheckForIllegalCrossThreadCalls property to false : CheckForIllegalCrossThreadCalls = false; :) :)
Have Fun Never forget it
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The "Tricky" way is just like carbon_golem suggested (and this is the correct way, u need to thank golem :):) ) the simple way and not recommended is override this by only changing the CheckForIllegalCrossThreadCalls property to false : CheckForIllegalCrossThreadCalls = false; :) :)
Have Fun Never forget it
Thank you very much half-life. :):) But is it really safe to do?? I mean what you suggested did work 100% but I read on Internet that this is used for Debugging, just to avoid error messages! :confused: I think someone should write article about Multi-threading on CP. I searched but didn't find any.
- Stop thinking in terms of limitations and start thinking in terms of possibilities -
modified on Monday, April 7, 2008 2:52 PM
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Thank you very much half-life. :):) But is it really safe to do?? I mean what you suggested did work 100% but I read on Internet that this is used for Debugging, just to avoid error messages! :confused: I think someone should write article about Multi-threading on CP. I searched but didn't find any.
- Stop thinking in terms of limitations and start thinking in terms of possibilities -
modified on Monday, April 7, 2008 2:52 PM
Nothing is Stupid When u do not know it The Property is MS Idea so it's probebly doable The right way goes like this:
//Declare a Deleagte for the type of the Function u will use //see that that if i had an //public void function() //so the declartion of the deleage would look like this : //public delegate void RefToFunction(); //without the parameter **public delegate void RefToFunction(string s);** //create an instance of the delegate like this: // and give it the function u like to invoke **RefToFunction handle = new RefToFunction(UpdateTextBox);** //declare the param an wrap it in a object array **string s = "Test"; object[] param = { s };** //Invoke with the handle and the param //where u need to invoke it //if u did not have any param so just : //this.Invoke(handle); **this.Invoke(handle, param);** //the implemntation of the function **public static void UpdateTextBox(string s) { MessageBox.Show(s); }ode> i did a lot of research about this so i hope i helped if u need any clarification just reply :):) Have Fun Never forget it ** -
The "Tricky" way is just like carbon_golem suggested (and this is the correct way, u need to thank golem :):) ) the simple way and not recommended is override this by only changing the CheckForIllegalCrossThreadCalls property to false : CheckForIllegalCrossThreadCalls = false; :) :)
Have Fun Never forget it
don't set CheckForIllegalCrossThreadCalls false, this is a terrible hack, that WILL result in malfunction, sooner or later (sooner if you are lucky). :)
Luc Pattyn [Forum Guidelines] [My Articles]
This month's tips: - before you ask a question here, search CodeProject, then Google; - the quality and detail of your question reflects on the effectiveness of the help you are likely to get; - use PRE tags to preserve formatting when showing multi-line code snippets.
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don't set CheckForIllegalCrossThreadCalls false, this is a terrible hack, that WILL result in malfunction, sooner or later (sooner if you are lucky). :)
Luc Pattyn [Forum Guidelines] [My Articles]
This month's tips: - before you ask a question here, search CodeProject, then Google; - the quality and detail of your question reflects on the effectiveness of the help you are likely to get; - use PRE tags to preserve formatting when showing multi-line code snippets.