Adding An Item To A List Control On Another Form From A Different Thread?
Apr 25, 2012
I've got a TCP Listener running on a separate thread. I want to have it log the incoming and outgoing messages in a list on the form instead of in message boxes. I've been reading about multiple threads, and I know there's something extra I need to do because form controls are not thread safe.
Unfortunately I've tried several tutorials on delegates and invoking but it still doesn't seem to insert the log items to the list. I even spent $60 on this Mastering Visual Basic 2010 book to "Build Rich Client and Web Applications with Visual Basic", but there isn't a single chapter on how to handle multiple threads.
I am trying to add a picture box to my form that contains an animated progress gif, in a separate thread, but I can't seem to get the picture box to appear on the form. Here is my form
vb.net Dim NewsItem As New ListViewItem NewsItem.Text = reader("Title") NewsItem.Tag = reader("NewsID") NewsItemList.Items.Add(NewsItem)
I'm looping though results in a db and adding items to my list view however i it's adding like tihs
ListViewItem: { Title showing here } ListViewItem: { Another Title showing here } ListViewItem: { And AnotherTitle showing here } What am I doing wrong it should just read
In one application, I need use 4 simultaneous threads.When the threads finished, I need to update the text of a TextBox.So, I create 4 Textbox, and I wanna the threads change the text to FINISHED.Each thread change one distinct TB.I use this "example"
Dim Terminados As Integer = 0 Private Sub frmEnviarMensagem_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Timer1.Enabled = True Timer1.Start()
[code]....
The problem is, I have an error in the red lines.The error is: INVALIDOPERATIONEXCEPTION "Cross-Thread operation not valid: Control tbPlaca1 Accessed from a thread other than the thread it was created on."I don't use cross threading. Each TB only was accessed for the correspondent thread, and for the "main program".
"Cross-thread operation not valid: Control 'Panel1' accessed from a thread other than the thread it was created on." The reason I am getting this error is because I am opening up a new form and then calling these three things:
Panel1.Show() Label1.Show() Label2.Show()
why I get this error message because it doesn't occur normally if I open Form2 after closing Form1, it only occurs when I open Form2 after closing Form4.
When my client try to connect to server I'm getting this error : Cross-thread operation not valid: Control 'l_users' accessed from a thread other than the thread it was created on.
Private Sub _socketManager_onConnectionAccept(ByVal SocketID As String) Handles _socketManager.onConnectionAccept l_Users.Items.Add(SocketID) End Sub
Would anyone be able to help me here please. I'm fairly new to VB.net and threading so im just trying to figure out what is happening.When I debug this I am getting the error thread operation not valid: Control 'ProgressBar1' accessed from a thread other than the thread it was created on.
I'm a little lost as to why the error is occuring or how to fix it. I've had to put the progress bar in a separate thread otherwise the GUI crashes
I have written an application that loads a form - frmCad as well as AutoCad. It does this via a class which detects when AutoCad quits.
Friend Class CadApp Private WithEvents AppObject As AcadApplication... Private Sub AppObject_BeginQuit(ByRef Cancel As Boolean) Handles AppObject.BeginQuit RaiseEvent Quit() End SubEnd Class
My main class loads frmCad as well as CadApp.
Public Class Cad Private WithEvents frmCad As CadForm Private WithEvents app As CadApp... Public Sub ShowForm() If frmCad Is Nothing Then frmCad = New CadForm frmCad.Visible = True End Sub... Private Sub app_Quit() Handles app.Quit frmCad.Dispose() frmCad = Nothing .... End Sub
When I debug the program, it stops at frmCad.Dispose()The program continues to execute, but all the code after it fails to work.Looking more carefully I get an error message which contains:-Cross-thread operation not valid: Control 'Autocad' accessed from a thread other than the thread it was created on.
My error:Cross-thread operation not valid: Control 'label2' accessed from a thread other than the thread it was created on. I want to be able to give my Public RunBot() sub access to edit Labels, buttons, etc without an error.
My problem is Cross-thread operation not valid: Control 'statusHO' accessed from a thread other than the thread it was created on.
System.InvalidOperationException was unhandled Message="Cross-thread operation not valid: Control 'statusHO' accessed from a thread other than the thread it was created on." Source="System.Windows.Forms" StackTrace:
[Code]...
i used it and it works fine then. but as it is mentioned its not a good practice to use it. So what should i do? is it ok if i use this as i am not able to use correct practice. Mine application is not for enterprise purpose. its just my class project, and it works fine even if i put application working in background. System works ok. I dont know how to correct this error.As i dont have that much knowlege of threads.
So please guide me how to fix this in correct way otherwise i am force to go for bad programming practice Please refer to Windows Mobile Developer Center > Smart Device Development Forums > Windows Mobile Development > Appendtext not working for all my code details
I'm new to databasing. How do you make it so you can add an item to a database on a form, Then follow a link to another form which has the database on, then what you put in on the previous form will be there?
How's it done? Sorry - Haven't been using VB very long >.<
just wondering if it is possible to have a form and then load up a control on that form but so it runs in a different thread to its parent... i tried:
[Code]...
But it still seemed to be running on the form's thread And just so you know ctlMTTest is just a control that has a button on it, that, when you click the button, a loop runs.
I have a list box on the form which functions as a copy/paste. When you copy something, it is automatically added to the list box as a "clipboard helper". Here is the problem,however: if the text is more than 1 line, the list box does not show all the text.It ends up looking messy.So getting back to my question, is it possible to make the list box item height for an item depending on the amount of lines that item contains?This is a one line sentence in the list box and should take up one line.This is a multi line sentence in the list box and should take up two lines for item height.
I'm learning VB.NET coming from a VB6 and Java background.In my app, I've got a function that validates the fields on a form. All it is doing is reading them, not updating. I've searched and see info about the backgroundWorker class, but all the examples are about updating the fields.I understand the idea of threading and how it works, but have never written code that spawned threads myself. I've always let the language handle it. It seems like a lot of work that I would have to write a sub using the backgroundWorker for every time I wanted to read or update each field. The couple of books I've got that introduce you to the language show you reading or updating the field directly.How do I know what threads are running other than writing the code like I'm used to then running through debugger to figure out what variables are on which thread?
Regarding my college project. i'm working on a sales system . i have a form which consist of all the following information( item code , item name , item price , quantity of item ) which is display using a data grid . data input by user using text box and all this information will be stored in a database(sales database) i'm using ms access 2007. the grand total will be displayed in a text box . and amount paid will be input in a text box too , my major problem now is how to i create a reciept that will have all this information of the purcase. i have a reciept button . what the next step ? i dont have any idea how to get the reciept done.
I have a windows application with a main form, on which a user control is added dynamically when a device connects trough USB.
On a user control, there is a thread wich is getting data from the device trough USB and when it is finished, I want to change a progressbar that is located on the main windows form where user control reside.
This is the code that is I call on the user control thread to change the progress bar value:
Frm_Main.UpdateProgressBar(CInt((AllBytesReceived / MaxBytesInFlash) * 100)) and this is a code that is called on the main form: Private Delegate Sub UpdateProgressBarDelegate(ByVal value As Integer)
there's a list-box with items, and say you want to modify an item in the middle of the list. You select that item and click "Modify" button and a new form appears with the previously selected item data from first form ready to be modified in a text-box. After modifying and clicking Ok the second form suppose to return that modified string to the first form and insert the modified string into the same spot instead of the originally selected item, so it looks like it was edited to the user.
When i run the program i am getting the following error in this line TextBox1.Text &= "File Created: " & FullPath & vbCrLf"Cross-thread operation not valid: Control 'TextBox1' accessed from a thread other than the thread it was created on."
I need your help on the following. In debugging mode only the program is stopping to the following line "My.Forms.FormMain.HelpProviderMain.HelpNamespace = "Reports.chm"" with the following error ""An error occurred creating the form. See Exception.InnerException for details. The error is: Cross-thread operation not valid: Control 'FormSplash' accessed from a thread other than the thread it was created on.""
I noticed that when I am putting NONE in SPLASH screen option in the properties of the project, there is no problem.I am no familiar with treating that's why can you give me detail instruction how to overcome this annoying problem?
In debugging mode only the program is stopping to the following line "My.Forms.FormMain.HelpProviderMain.HelpNamespace = "Reports.chm"" with the following error ""An error occurred creating the form. See Exception.InnerException for details. The error is: Cross-thread operation not valid: Control 'FormSplash' accessed from a thread other than the thread it was created on.""I noticed that when I am putting NONE in SPLASH screen option in the properties of the project, there is no problem.
I am using the template for the login form provided by Visual Basc 2005. I want to add a list box or drop down menu to it for the user to be able to select the desired server to connect to. Is this possible? I have tried declaring a listbox and then adding it to the form but it did not show up.
