Cross-Threading And Listbox?
Dec 15, 2011
I've problem with my application. I have one class frmMain, where I have one Listbox. I'm developing a separate class that lunches a couple of threads. They do some work, and in the end I want to show the data in the frmMain listbox. I'm using the following code:
One sub that handles the requests to the Listbox. I declare it in Module
Module Functions
Public Sub ChangeText(ByVal ctrl As ListBox, ByVal str As String)
Try
If ctrl.InvokeRequired Then
[Code]...
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Dec 1, 2010
I have this situation where I want to set the visibility property on the form but I have a cross threading issue. I have coded it like the following but is it possible to achieve it on the property on itself.
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Aug 8, 2010
I have an application with two forms - a splash form and the main form. The main form reads an XML file and displays data from the file in a rich text box. While that is happening the splash form is displayed. When the main form is ready to be displayed the splash form closes and the main form is displayed. I have a progress bar on the splash form to inform the user of the progress of the load. I want to set the maximum value for the progress bar to the number of elements in the XML file. In the main form I am using a reader to count the number of elements. After I get that number I wan to update the maximum on the progress bar control so it displays correctly. That is where I am getting the cross threading error. Now I could do that in the splash form. But where the real issue lies is I want to update the progress bar value every time I read an element in the main form process to read the XML file. That I don't think I can do in the splash form as it would duplicate the process of the main form and defeat the purpose of the splash form.
I have researched this issue but can't find an answer. I have tried the delegate route but I still get a cross-threading error. I assume that is because I am cross threading across forms.
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Oct 27, 2010
I'm using Visual Basic 2010I've created a ListBox and a BackgroundWorker using designerI want to change the location of listbox using backgroundworker but I get the error as follows:"InvalidOperationException was Handled by user code:"Cross-thread operation not valid: Control 'ListBox1' accessed from a thread other than the thread it was created on
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Jun 22, 2011
I am a student attempting to learn VB.NET on my own. Today I wanted to tackle the BackgroundWorker component. I found an excellent article online: How To Use a Background Worker. I successfully completed the walkthrough and even performed the "adventorous" part that dealt with working with controls updating across threads using delegates.Now I came to a part that I didn't understand how it was working. To summarize the following code, I have a delegate that has a Label and a String in its signature. I then have a subroutine that is called on the worker thread. Inside this subroutine the delegate is created and (I guess) ran again so that it is on the same (Main) thread. Please correct me if I'm wrong here.
Here is the method is performed on the worker thread:
Private Sub My_BgWorker_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles My_BGWorker.DoWork
[code].....
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Sep 28, 2010
I've been reading around trying to find out why I'd be getting this exception to no avail.
I'm using Visual Basic 2010.
Briefly, I have a "Settings Panel" form which takes a while to create (it contains a lot of labels and textboxes), so I create it in another thread.
After it's loaded, it can be viewed by clicking a button which changes the form's visibility to True. I use the following subroutine to handle invokes for my controls:
Public Sub InvokeControl(Of T As Control)(ByVal Control As T, ByVal Action As Action(Of T))
If Control.InvokeRequired Then
[Code]....
The SettingsTable.Create() method generates a bunch of Labels and TextBoxes based on the contents of the application settings and adds them to the SettingsTable.
When I click on the ViewSettingsPanel checkbox, I get a cross-thread violation error.
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Nov 9, 2009
I have a relatively simple question regarding the best way to call the DataGridView.Rows.Add function when it is inherited into the current control. Which is the best way to make the call to the inherited control? Call it directly in the invoke or call it using recursive-like function? They both seem to produce the same result, a row gets added and the quantity is returned, but which is the most efficient?The delegate: Private Delegate Function ReturnDelegate() As Object
The two ways are:
A)
Private Overloads Function AddRow() As Integer
If InvokeRequired Then
Return CInt(Invoke(New ReturnDelegate(AddressOf AddRow)))
[code]....
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Aug 25, 2009
I looked around the site and the questions I found relating to this subject were for C# (the application that I am maintaining is written in VB.NET), so I apologize if I overlooked one. Here is where I am calling my thread:
[Code]...
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May 15, 2009
I've not got any issues with Cross threading but I hate the amount of work involved in sorting cross threading issues out.I thought today that my inherited Listview Control could have built in cross threading capabilities; it would decrease the amount of work on the form, and tidy things up.I've got this to work (EnsureVisible method), BUT I'm a little stuck when it comes to the Items.add below is my example control.
[Code]...
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Feb 10, 2010
I'm adding multi-threading facilities for the first time. I have a function that is wrapped to be run in a separated thread. This function retrieves data (text) from a combobox and it works for sure without multi-threading.
When I call it as multi-threaded, I get the following error when I try to retrieve the data from the cmobobox: Cross-thread operation not valid: Control 'cmb1stBL' accessed from a thread other than the thread it was created on.
It looks like a restriction of thread-safety... I assume that the child thread cannot read from his parent, to make sure that he doesn't change his parent data. So how can I read the data from the combobox? Should I read the comoboxbox data before calling the child thread?
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Aug 18, 2010
i m working on an application where i m using multi threading.suppose i ve below threads
Thread1
Thread2
Thread3
so i want to call a method from some specific place where every thread running concurrently
[code]...
so i m not able to identify a thread in the case "ABC"
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Jun 9, 2011
I am unable to add data in my listbox its showing in msgbox but did not add in listbox i try using richtextbox but again same prob.[code]...
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Jun 8, 2009
I am using VS 2008 Pro and my ? is, I am trying to add lines to a listbox and keep getting Cross-Thread Operation not Valid exception. The code I am using was downloaded from codeproject. When I run this app, it works fine. I added it to my app and this is where the cross-threading problem occurs.[code]I am trying to convert mp3 files to .wav files. With the line above it works. With it out, the exception is thrown.
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Nov 19, 2009
If I set a ListBox.Height = ListBox.PreferredHeight when the control is hidden and IntegralHeight = True, then set it visible:
a) Actual Height reduces by typically 3-5 pixels after redraw (but not 1 pixel per item).
b) PreferredHeight does not not appear to give the correct integral of item heights.
Is there a way to make ListBox calculate the correct integral Height before the ListBox is made visible, so it can be correctly pre-positioned from bottom edge?
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
ListBox1.Visible = False
ListBox1.IntegralHeight = True
[CODE]...
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Feb 17, 2011
This code bellow to compile a single listBox on form1 to listBox on form2 then listBox on form3.
I want to modified this code to compile 169 of ListBoxs on form1 to 169 listboxs on form2
and 169 listBoxs on form3.Try this code,not need the new coding.
Original code from JoOl and modified by John Anthony oliver
[Code]...
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Feb 13, 2010
1 when my listbox returns resaults it only brings back 10 how do I set it to return lets say 500
and question 2 is when I click on my links in listbox it's not opening webpage as I would expect it...
This is my code
[Code]...
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Jun 15, 2010
I have a DataGridView that is being filled with data from a table. Inside this table is a column called 'group' that has the ID of an individual group in another table.
What I would like to do, is when the DataGridView is filled, instead of showing the ID contained in 'group', I'd like it to display the name of the group. Is there some type of VB.net 'magic' that can do this, or do I need to cross-reference the data myself?
Here is a breakdown of what the 2 tables look like:
table1
id
group (this holds the value of column id in table 2)
weight
[code]....
BTW - I am using Visual Studio Express.
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Apr 19, 2010
I wish to use common CRC logic in a VB.NET or C# application as well as on a C/Linux application. I have one C/Linux application that interacts with a webservice (written in C#) and also a web application (written in VB.NET). For some data, I want to add a CRC to the data itself (say a file) from the .NET side and check for the integrity of the data (checking the CRC) on the client - and also vice-versa.
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Mar 31, 2011
I'm thinking of porting my application from VB.net to the C# based MONO project, so it can run on both Windows and Mac. However, I am in need of a Mac-friendly alternative to WPF. It has to have very similar functionality. QML (by QT) is not a viable option, as it costs far too much money for us.
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Aug 4, 2009
I have a interesting problem: Where I work we've built a home-grown ERP system in VB6 that we are slowly moving over into vb.net. There are some projects have are in .net: we have a hand-held C# project that uses a web service to talk to our database, I've built some reporting screens using Crystal and some smaller maintenance screens.
Well as we have been plotting the conversion out, we want to have a way to separate our business logic and UI so that the UI can be a win/web form or a Smart Device project. Is this even possible? I try to reference the DLL in a test I have and it gives me this error when trying to debug using a emulator Deployment and/or registration failed with error: 0x8973190e. Error writing file '%csidl_program_files%smartdeviceproject1system.windows.forms.dll'. Error 0x80070070: There is not enough space on the disk.
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May 4, 2010
this is sumit from Larsen & Toubro Mumbai-India,I am writing a code for some sort of software in which execution of some code is required as soon as my software receive a barcode from barcode scanner (serial input). Now through datareceived event handler i am able to read the barcode but after that i am not able to send this barcode to any textbox or even i am not able to start any other event like performclick to any button or anything. I am getting an exception as cross linking of threads not possible. please refer to the image and give me the solution asap.
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Jun 10, 2009
How can I cross reference a .contains for two textboxes? like
vb
for each word in textbox1.text
if textbox2.text.contains(word) then
msgbox("There was a word found that should not be there",msgboxstyle.critical,"Invalid")
end if
next
Would I need to do a RegEx to get every word in the textobox? Or should i just use a listbox and do a for each I as item in listbox1.items?
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Jan 27, 2010
im sorry if this has been asked before.but i couldent find it in my first look i have a form that runs a query on a mysql database but as it runs the query the form stops responding till it finishes sooo i had the smart idea of putting it in a back ground worker..
GREAT i thot i had it working it all seemed to go greeat then i noticed when i try to change the label text on the form to corispond to the info it got... it wont work it give me a cross threading error....
how to cross thread between the back ground worker and the origial form..
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Apr 5, 2012
I am getting this error: Unable to cast object of type 'SGA.AppContext' to type System.ComponentModel.ISynchronizeInvoke'.I am not using a start up for my project but a sub main() and a threaded class AppContext
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May 14, 2011
I am creating a CHAT interface for my game (when networking, server/client style) and I ran into a little problem..The way it works... I have forms for the SERVER (frmServer) and CLIENTS (frmClient) each of them have a LISTBOX (lbChat) in which I input (lbChat.Items.Add(string)) text as the users type it - in essence a chatbox...
So, let's use the CLIENT as an example (as it is simpler and the concept the same in both client and server cases)The Client form (frmClient) creates a thread that is used to listen for chat messages (via TCP) - so what I did was pass the listbox itself (lbChat) to the thread thus (I thought) solving my problem of writing into the listbox when chat messages arrive (and are caught by the thread and not frmClient of course)Now while debugging the code I get the following exception when my thread attempts to write in the listbox (lbChat) of frmClient General Exception: System.InvalidOperationException: Cross-thread operation not valid: Control 'lbChat' accessed from a thread other than the thread it was created on.
So now the question is how do I work around this cross-thread exception? How do I pass information (chat text) from my listener threads (and there will be multiple of them in the field, one per client) to the centralized listbox (lbChat) on the form?I need some kind of method to transfer information while also reducing the chances of running into contention issues (do I need to use ReaderWriterLock?), thing is I have no clue how to accomplish this task (I thought simply passing in the listbox would allow me to write to it in each of the threads).
[Code]...
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Jun 16, 2009
I'm co-developing a vehicle information system that reads and presents data from a communication bus. Signaling information on the bus is stored on some kind of database (from the dark ages i'd guess) from which it's only possible to get data out of by extracting a xml-snapshot. Since that wasn't bad enough, someone in upper management thought it was a great idea to treat different parts of the system as different projects (it looked really nice in the organizational chart) which lead to more databases...It is now my responsibility to merge these xml-files into one and before I start banging my head against the wall i thought it would be a good idea to check with you geniuses if there's any neat solution to my problem.The structure of the xml is somewhat like this:
<data>
<frame ID="1001">
<attributes>
[code].....
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Mar 12, 2011
I have a file that is being generated automatically on a server in a Windows domain, say, called, "prod" and I will need to have VB.NET to transmit this file to another server in another Windows domain, say, "QA", where QA and Prod have different credentials altogether and I have to authenticate that credential every time I opened up the destination folder.Therefore, I guess the regular filecopy method would not work?
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Apr 11, 2010
I'm trying to do a basic function, I'm using Visual Basic 2008 express, I have a windows form with 1 textbox, 1 button and a serial port. When the button is pressed serialport1 is opened then the data received is trimmed to remove unwanted char from start and end and then is displayed in the textbox, when the button is pressed again the port is closed, this works fine but in debug mode I get a cross thread error, telling me I can't use textbox1.text=result
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May 22, 2012
I am trying to load data using a backgroundworker using a code snippet that I found. I think that it would all work fine, except that I am getting an error that I am doing a cross thread operation. The task that I am trying to accomplish is loading data for a large dataset when a command (Run Operation) is called so that I can prepare the user that it may take a long time, and I can display a scrolling marque to show them that the program is not frozen. I am using a separate form to display the warning, an OK button, and a scrolling marque.[code]
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Oct 14, 2011
I am developing a application called filecopy(windows application). Inside the form1.vb i am having progressbar. Having one more class called FileCopy. inside the filecopy class i have DirectoryCopy method. it invoke the percentage calculation method(that is in form1.vb) for how many percentage is completed. Each and every time the value. Finally , the percentage value is assign to progressbar.value. AT that thime i am getting cross thread operation is not valid exectption. This is my code;
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