look at the comments at the beginning of each class. Note, the period is rather small (100ms), and the process being triggered could occasionally take more than 100ms (in which case, the next thread trigger should be delayed ... two threads shoud never overlap). Also, the class will never be instantiated more than once.
[Code]....
What's the easiest way to run a periodic task in the background in VB?
For example: Update a label every second with the current time, while still allowing the form to be available.
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".
This is the error message I am getting:
"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.
I have done a program using vb2005 to display reading from my microcontroller bs2 board but have encountered some problems. My code are as follows.
Dim Stop_Rx As Boolean
Private Sub btnRead_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnRead.Click
SerialPort1.Open()
[code]....
I've encounter an error which is, (Cross-thread operation not valid: Control 'txt1' accessed from a thread other than the thread it was created on.)
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
[Code]...
My understanding is that thread.join will suspend the execution of code on the calling thread until the spawned thread finishes or is aborted...
With that in mind, I tried this:
For i = 1 to 50
threads = New Thread(AddressOf test)
threads.IsBackground = True
threads.SetApartmentState(ApartmentState.STA)
[CODE]...
However, the rest of the code runs when the loop finishes, not waiting for all the spawned threads to finish. Since the rest of the code needs the threads to finish (otherwise the rest will error).
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.
[Code]...
I'm getting the 'System.InvalidOperationException' error on acccessing a thread from other than where it was created. My code is:
'Required by the Windows Form Designer
Public components As System.ComponentModel.IContainer ' changed from private
[code]....
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
Cross-thread operation not valid: Control 'lv1' accessed from a thread other than the thread it was created on.
Dim lvi As ListViewItem
For Each lvi In lv1.Items
[code]....
The drive is connected via USB and the problem I'm having is that, periodically, while my code is executing, the usb drive seems to disconnect and reconnect. (Nothing to do with the program, but the drive itself).I want to find a way to prevent these temporary drive reconnects from interrupting my code. IE, i want to insure that whatever read or write that is requested is actually executed even in the case of a temporary drive interruption.
View 1 RepliesOk i have a Form with the following
Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
txtNotepad.Text = LoadFile("notes.txt")
[code].....
How add a timer with different intervals like ( 1000,5000,10000) ? , I need all intervals in the same timer.
View 6 RepliesWhat would I do to change my intervals into minutes?
to have my timer set to 10 minutes?
I decided to whip up a simple stopwatch-esque timer for some needs of mine. Well after writing a very basic code for the timer to show seconds and milliseconds I see that the intervals are wrong[code]...
View 16 RepliesI have a piece of hardware that is controlled via USB.There are 8 LEDs on the output byte. One LED per bit.I like to toggle the outputs based on selection of checkboxes and given frequency entered in TextBox.I inserted 8 checkboxes to allow me to select the desired LEDs to be on.I select the checkboxes to select the required LEDs.The checkbox gives me the byte value. XORing the byte value with 255I can see them toggling very fast. I have a while loop to blink forever until I click on stop button.The stop makes the seq=false and this should stop the blinking but it keeps going.How can I insert desired delay of flashing frequency in my output routine?How can I stop on demand to change pattern without exiting the program.
View 2 RepliesI'm using the chart control that's built in to Visual Basic 2010.NET Service Pack 4.
I am creating a basic date time graph with time on the axis and, at the minute, random points between -20 and positive 20 on the y axis. At the minute I can set everything up perfectly. The only problem is that the label on the x axis is not a time, it's a number. To be precise, it's the XLabelInterval value. This value is a double, so the label on the x axis is also a double not a time. But that's only interval I am setting. I think, by default, because I am not setting any labels, it is just using that value as the label as well.[code]...
What are the timer intervals for VB2008?It wont let me go over 100 so I'm not sure if 1= 1 second, or what.
View 2 RepliesI am busy with a routine that will draw a bar chart.The X-axis is from 0 -100, no problem. The problem is the Y-axis.it will range from 0 to whatever the highest y-value will be.
My problem is that the y-axis should still be divided into 10 intervals, and the lenght of my y-axis should be the same in my picture box.I am using an array to fill the values, chartdata (0-9). It gets 10 values from the program. the values are 0 -10, 11 -20,21-30....91-100 . here is the code. It is working, but my Y-axis is messed up. Printing the labels of the y-axis is a problem.
Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
Dim chartData() As Single = {mark0, mark10, mark20, mark30, mark40, mark50, mark60, mark70, mark80, mark90}[code]......\vb
This is my code atm and it wont change the interval at all[code]...
View 22 RepliesI have a windows forms project in VS2010 with a simple line chart.The data is dynamic and always ranging between 1.4000 and 1.5000.I want the Y axis's gridlines/labels to always be displayed on every #.##20 data point, as in: [code] So I tried the Interval property for the axis gridlines/ labels, setting it to 0.002, and the result was that the gridlines/labels were displayed every 0.0020 points, like for example this: [code]
but not on 0.0020 points too as shown previously.
I have two webbrowser controls in my application, and I need them to refresh every so often, for example, every 5 minutes. How do I do that?
View 4 RepliesI want to upload data at regular intervals, for that I used windows service with timer. Now problem is when I start my service. Its showing System.IO.IOException error.
View 8 RepliesI have created a windows service and I have two different timer variables in there. 1st one fires off every 5 seconds and then does whats it is required to do. The second one fires every 30 seconds.
I make sure that when the function are getting executed I disable both the timers and enable once the function is complete.My problem is my second longer (30 second ) timer never fires only the first one is firing. I had created this service 3 months ago and it was working fine till now. But now I do not see the timers work properly in a simple windows app i created to test their workings.
[Code]...
i have a need for my vb.net app to perform methods at regular intervals. it needs to check sql tables and react to data found, send email and sms messages. i've tried using a loop but this only allows me to perform 1 check ie checking sql tables. the app needs to execute a method every x minutes. i tried using system threading but i got errors.
View 1 RepliesI want to generate random numbers at regular time intervals. I am putting the random generation in a loop which works when a button is clicked. But since the Timer itself is a control, I don't know how to do it. I tried putting the timer in a module so I can access it inside the form.
But the following error occurs:
"Error 1 Handles clause requires a WithEvents variable defined in the containing type or one of its base types".
When I doubleclick the timer icon the code appears as follows.
Public Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
End Sub
I need to fill a combobox with times at half an hour intervals:
12:00 am
12:30 am
1:00 am
1:30 am
all the way to 11:30 pm.
I could do it all manually, for next loop, cur hour, cur min, add 30 min, when over 60 add hour and so on....
but there has to be an easy way to do this?