Access A Component In Form From A Thread Created In A Different Form?
Jun 18, 2011
I have 2 forms main_frm and copying_frm. In main_frm, there is a list view that is populated with file names. The user then clicks save and all the files in the list are copied to a folder that they choose using a folder browser dialog. When this happens, I do copying_frm.ShowDialog() to display the copying_frm. The copying_frm contains a progress bar and a cancel button. I can get the progress bar to indicate how much has been copied. But that freezes up the application. To get around this, I create a new thread (called copyingThread) that copies the files. When that thread runs though, it can't access the waitingList_lvw in main_frm. For example, in the function that the copyingThread executes, if I have this line of code: MsgBox(main_frm.waitingList_lvw.Items.Count.ToString()) the result is 0. Also, I don't get any errors and no files are copied. How do I access waitingList_lvw in main_frm from a thread called copyThread that was created in copying_frm?
I have an app (vb.net) that sues multi threading and have tow problems.
1. The program is used for trading currency markets and mointers prices all day. When a signal is generated it wil place a trade in a new thread. In the new thread it checks to see if a trade is on already and if so it will not place another trade.The problem is it can be too fast and place another trade before the server has processed the first trade. So trade count returns 0. As the system watches 6 accounts I can not just pause the other thread to make sure it has finished before trying ot place another trade.How to i check to make sure the first thread is finished so when i check for trade count it retuns 1?
2.The new thread is inside a class and has a logging class as well. The problem is writing to the text box on the main thread. As the logging thread is created in the new thread it has no access to the textbox. I have tried using invoke but it still does not write to text box as it does not exist in the new thread.How do i reference a form from a class that was created in a new thread?
I am converting an old Vb6 solution to .net 2.0 in vs2010. I've been working in C# for about 3 years now and .net for 5. I don't recall having this problem in C#, but if I want initialize a readonly collection of DerivedControlFoo Is there a clean way to do it besides creating a sub to do it all off somewhere else? I'd love to be able to do it at the class level at the declaration for readability and simplicity.
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)
I was a vb6 user, done a few projects only with forums Now i am moving to vb.net(vb2010) and i have some trouble.Lets say we have a form(form1), a module(mod1) and a textbox on the form1.
i want to start a Sub (DoWork) in the module but in a new thread.
Dim Thread1 As System.Threading.Thread Thread1 = New Threading.Thread(AddressOf mod1.DoWork) Thread1.Start()
The DoWork sub does some stuff and when it's finished i want to change the text of a textbox1 in the main form and start another sub (DoWork2) on the main form under the main thread not the one DoWork is running under.
Plese do not refer me to another post that mighe give me a part answer, try to explain to me what i have to do and why.
Create a DLL component for database operation and use created component in another project. Required methods, events and properties
a. Connect b. Add c. Delete d. Save e. Record navigation (first, next, previous, last) f. Properties for all database fields g. Events for validation of database fields.
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
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim textbox1 As New TextBox
[Code].....
When this row GroupBox1.Controls.Add(textbox1) and GroupBox control are being deleted from Form, the TextBox isn't created on the Form after the event is fired.
How do i load the Main form of a WPF so that a seperate thread goes and gets data from the database while the form is in an apartmentstate? (drag-able / movable) I Know this is possible with opening a new window from your main form like this :
Private Sub openOrderWindow() Dim OrderWindow As Orders = New Orders OrderWindow.ShowDialog() End Sub
[code]....
I've tried putting MyBase.ShowDialog() and .Show() and .9000+ other things The only benefit I've got out of using a seperate thread to load from the databse is i can see the screen right away (as oppose to it being a transparent box until it loads) but i cannot move it around or minimize it?is there any way to make it Movable while it loads?
In the main form the user can choose to download information from a device.Since this request takes time, when "download information" is pressed I open new form in a separate thread: Private Sub RunDownload()
it's just for a program registration. i would store all of the registration codes in the access database, then export it to XML, then upload it to my web host. I would then somehow connect it to my Visual Basics login form (Which I have already made). If this can't be done, having them register through the form and having all the allowed codes on the internet (So i can easily edit them)!
I have a series of methods being called for my networking code. An event gets fired from the networking thread. Inside this event, which I've hooked into from a singleton class, I route messages to form level methods which they register on form load to handle certain messages they care about. Inside of these form message hooks I need to close the current form (which I was able to do) but also show a different one (which is giving me the trouble).
I am currently working on a project that has a splashscreen This splash screen is designed to be shown when the main form begins to load its requirements, and then closes once it has loaded... Currently it works like so:
Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load frmSplash.Show() dolotsofloading() frmSplash.Close() End Sub
My program crashes with the following error:Controls created on one thread cannot be parented to a control on a different thread.Purpose of the program is to add a control from a thread outside the main thread.Below is the code Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
I have a few forms that have a lot of really intensive updating along with a great deal of user interface (text boxes, button clicking etc) Is it possible to open a separate form as a separate UI thread from the start up form that called it to "show" or open or whatever the new method might be?
I have a VB.NET form created in VS 2008. This form contains an ActiveXControl (MapPoint 2006 Europe ocx) located and reference here:[code]The project compiles just fine. However, when I run this starting form I receive this error:An error occurred creating the form. See Exception.InnerException for details. The error is: Cross-thread operation not valid: Control 'AxMappointControl1' accessed from a thread other than the thread it was created on.[code]I mention that the very same project was upgraded from VS 2005 on which worked just fine.
I would like to save a form to complete in the properties of "My.Settings" Is this possible? [code]where my.setting.form2 is a system.windows.form. form.it is possible to do that ?
