Cross Link Two Different Threads?
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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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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Feb 8, 2010
My application need to communicate with my self made device through serial port. I have to change the selected index of Tabs when I press a button on my device. I have Form1, Form2, Module1 Form1 Contains the Serial Port Control. Form2 contains the Tab which needs to be changed. When I press a button on device them, the button pressed is stored in an integer form in a global variable.The Interrupt for the Serial Port directs the control to the module1 where I decide using Select Case that what index of which TabControl I have to select.Depending on that, I change the Index of the required Tab.
PROBLEM:cross thread exception is fired as soon as the control reaches the statement where I Modify the SelectIndex property from the select case at Module1.While, on my other PC, the SelectIndex property is changed, but the next tab is not shown.
BUT, if I put all this code in a button control, and try to activate from there, then it works perfectly. However, I have to navigate through the tab controls using my self made device.I searched a lot on net and came across a solution which describes that we have to use delegate function and invokeRequired methods to ensure that the procedures run on the same thread.I am not able to decide that where exactly shoud the code for delegates and all be written, in form1, or form2, or module1.Also, in the hit and try that I did, I always got the value of InvoleRequired as False.
Here is the part of Code that I wrote for Delegates
Code:
'Form 1 is BLINDHELPER_SIGNIN
'form 2 is BLINDHELPER_USER
' I have defined these at Module1
Public Delegate Sub DeleToManageTabs(ByVal tb As TabControl)
Public Sub manage_Tabs(ByVal tab As TabControl)
MsgBox(tab.Name)
[code]....
After using this code also, there is no change in working of my application.
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Feb 5, 2012
Frankly, NONE of this makes sense to me..[URL]..They just jump right into code without baby steps that explain the situation.Every other aspect of VBnet has been well spelled out to me and I get it -- but this business of using the serial port and going nowhere because of a cross thread error has me 100% baffled.
If anyone can point me to a tutorial that really explains it simply and well (without jumping into friggin' code).Even in the above link, they show 3 different techniques of addressing the same problem ! (Like I CARE
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Jun 29, 2010
[Code]...
This was the code and this is the thread HERE Ok its working and everything but when i want to perform something when click is noticed it says i cant cross-threads
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Apr 15, 2010
i want the label1 text changes with the link that the mouse cross above him.
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Oct 19, 2011
I just had a new, last-minute idea on to take on a task, so I am running to StackExchange for quick help.
What I want to do is execute a series of methods right in a row, each in their own threads. I want the application to wait until all of these threads are completed, after which the program will resume. It also has to use managed threading (thread pool).
What quick examples could you provide to help me along the way? If it's too complex, what things should I know about so that I can Google it on my own?
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Dec 30, 2009
I have a main thread which is designed to be a batch processor - it spawns a series of 'child' threads from a loop (which can vary in terms of the no of items) - see below
[Code]...
However, each of the 'child' threads could take anywhere from milliseconds to about a minute to process - depending on the complexity of each calculation. There may also be a large number of child threads - e.g 100s. Creating large numbers of child threads is not efficient. I therefore want some way to effectively queue each child thread (and cancel if the process is taking too long to complete). Autoevents seems like one way of doing this, but the only examples I can find seem to assume there are two different processes on seperate threads, not one process being repeated.
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Dec 4, 2010
I'm using visual basic 2010 express..I'm building my own web browser and want to add a download manager.I have been able to build one that will download a file if I type the file location into a text box.What I'm trying to figure out is how to have the download manager open when I click on a download link on a web page.How to make the download manager know it is a link to a downloadable file as opposed to something like a link to another webpage?
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Feb 8, 2012
I have a link here that works perfect for calling the postback close that I need to happen:
<a href="javascript:parent.__doPostBack('Close','')"><asp:Label ID="Label5" runat="server" Text="Close Me"></asp:Label></a>
However, I would like to be able to call the *javascript:parent.__doPostBack('Close','')* method from the code-behind file rather than the user clicking the link. I.e., when I have completed my tasks in the application code, call parent.doPostBack as my last function call, which closes the window in question.
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Jun 12, 2009
When a button is clicked i am creating HTML that will be displayed in the WebBrowser1 control. With this HTML are several links to other pages. Is it possible that when one of these links is clicked, that WebBrowser2 navigates to the page instead of WebBrowser1?
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Jan 30, 2009
I have a project that I would like to add a URL link and an email link to in the Help/About dialog. How can I do this? Is it possible to add HTML code to a VB project? This is not a Web application.
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Sep 4, 2009
Im trying to create a webbrowser in VB 08;
I was wondering how i would create new tab with the Link the clicked.
*EG* They Right-Click Link > Open In New Window/Tab > Makes New Tab In My Program > Navigates To The Linked Clicked.
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Dec 13, 2010
so I'm using Visual Studio 2010 and I'm trying to make a program where I would have a textbox where the user would type,then a "Go" button. In the textbox, the user would type a number, lets go with 1 for an example. A user would type 1 in the textbox, then it would automatically add the 1 to the end of this .swf link: "http:[url]... after they enter the 1 in the textbox and press the "Go" button, it would add the 1 to the end of that link, then that link would open a new shockwaveflash form with the link being the Movie. Is this possible?
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Dec 18, 2009
i am using this function to get link of page which refered current page (in Back Button)
[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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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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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.
[Code]...
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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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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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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;
[Code]...
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