Infinite Loop And Cross Threading?
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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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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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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Jul 12, 2009
1) Diff b/w nothing & string in terms of variable declaration.
2)Erase keyword.I have never heard of such keyword in mine whole 1 + yrs of exp.
3) Diff b/w functions & properties? I say,Functions return a value,But propertiesare used to set or get the values. He say properties also return a value.
4)How can we use a class as a datasource?
5)Partial Class? hey frnds above question is for C++ na.Or there is also such class in VB.Net.
6)When the error stack overflow comes?
7) How we can we make indefinite loop , without uusing any variable declaration.
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Aug 12, 2009
I made a game in VB .Net that uses tcp and sends messages back and forth.What is happening is, every so often, the message cannot be sent quickly enough, so then the TCPObj.connect() method goes into a loop, until it reaches the timeout and then spits out an error. Most of the time though, it never gets to the error, my application just freezes, and then comes back after TCPObj.connect() succeeds. How can I make the connect() method do application.doevents while it's trying to connect? Basically, I dont want it to freeze up my whole application. Since tcp.connect() is a .NET method, I can't go in and add application.doevents.
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Feb 24, 2009
Is it possible to write an infinite for loop in VB.NET?
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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 29, 2008
Code:
p = -1
Try
ListBox3.SelectedIndex = p
Catch ex As Exception
ListBox3.SelectedIndex = -1
p = ListBox3.SelectedIndex
End Try
Just cycles through my listbox without exiting the try. It keeps having an error causing the catch again.
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Dec 30, 2010
I am making a program thats going to be an msn style popup for reminders. I made an infinite loop to activate the popup when the date = current date. However its stuck in the loop and I cant run other functions while the loop is running. How can I get the alert to go off while also running the program?
Public Class Form1
Structure List
Dim Name As String
Dim Day As Date
Dim Hour As String
Dim Min As String
[Code] .....
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Feb 11, 2011
While building out an interface for patient/client lookup, we have a pull from out FoxPro EMR creating the patient table and populating the lookup on the EU interface.
[Code]...
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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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Sep 1, 2010
I am trying to use a Web Service to return Json for a Collection of Users from a Database Table. I'm only new to .NET (< 1 week experience), and I don't want to use the UpdatePanel for AJAX. I have tried using the JavaScriptSerializer as well as Json.NET to serialize. Both cases seem to spawn an Infinite Loop.[code]
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Apr 22, 2012
I'm bubble sorting an array called number which starts at (1) and ends with (6), the code I'm currently using is this:[code]
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Dec 10, 2010
I wanted to draw a chart on a picture box. So I create a form, put a picture box on it, and then in the code of Form_load, I put a handler to the paint event of the picture box. This seems to create an infinite loop, judging from the behavior of the form.
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Jan 27, 2010
Whenever I try to create a new CD object I get a stack overflow. I want a parameter to be passed into mediaFactory so that it could be determined what type of media is created. Why I might be having problems with this when I do this
"Dim media As CD = New CD()"
Public MustInherit Class MediaFactory
Inherits MediaContext
Implements IMedia
Public Sub New(ByVal typeId As Integer)
[Code] .....
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Oct 10, 2011
Following code is used in a .NET 2.0 windows service to continuously monitor a the table in the Database.[code]Seelctjob method will connect to SQL server 2005 database and executes the following Select query to see if there is a record with a particular status code.[code]This Select Query is executed continuously. If there is a record Start method will process further.I want to avoid executing the query continuoulsy. I tried using Sleep method and timer control. Thread.Sleep method stops the execution for sometime.[code]What is the best way of connecting to DB and monitoring a table at regular intervals of time without having much performance impact? When to use thread.sleep and a timer control and what is the difference between them?
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Jan 18, 2012
This code hangs in infinite loop. Any ideas why is that? Is that a bug in .NET? Can I do something about it?
Dim urlRegex As New
Regex("((?:[a-z][w-]+:(?:/{1,3}|[a-z0-9%])|wwwd{0,3}[.]|ftp[.]|[a-z0-9.-]+[.][a-z]{2,4}/)(?:[^s()<>]+|(([^s()<>]+|(([^s()<>]+)))*))+(?:(([^s()<>]+|(([^s()<>]+)))*)|[^s`!()
[code].....
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Jun 25, 2010
Im working with and trying to run an infinite loop on a new thread which at some point takes action (e.g. make changes to Viewport3D). But no matter what I use:
- BeginInvoke
- Background Worker
- Timer
I run into problems. My porblems are:
[Code]....
I am doing all this in WPF.
How can I run the loop in the background and get it to affect the Viewport3D controls content without throwing an error or freezing up the application? A Viewpoirt3D is a control in WPF.
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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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Oct 25, 2010
I am descending all the directories of my C drive to get a complete list of all extensions.When I get to: C:Windows.oldDocuments and SettingsAll UsersApplication Data
the program goes into a loop: C:Windows.oldDocuments and SettingsAll UsersApplication Data Application Data Application Data until the path exceeds maximum length (248 characters for the directory).
[Code]...
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Jul 26, 2010
As you all know, If the dataBase requires a numerical value then an error will occur when the user tries to insert the incorrect data type. With the code below after the user types in a value beside an int value type then it will go into an Loop through more than what is needed. How can I apply the same logic but allow the program not to check the 60 rows (I set the row size to 60). I want to break out of it if there are blanks ONLY if a row is blank and not for a black cell, because if the user leaves one cell blank then it would loop through the 'for each' for how many rows that they is. Initially there are 60 rows.
MIS
For Each item As DataGridViewRow In dgvLaser.Rows
If IsNumeric(item.Cells(3)) Then
Exit For
Else
MessageBox.Show("Check Record Count. Numerical values only..!")
End If
Next
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Aug 2, 2011
I am trying to create a program that the user enters the number of enrollments for 5 different campuses during two semesters. I just got started and here is what I have so far but when I run the program it is stuck in an infinite loop and will not go to the next function. I am not sure how to end the loop. Here is what I have so far:
Module Module1
Dim SIZE As Integer = 5
Dim campus() As String = {"Decatur Day", "Decatur Evening", "Huntsville Day", "Huntsville Evening", "Distance Learning"}
Dim semester() As String = {"Fall 2010 semester", "Spring 2011 semester"}
[Code] .....
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May 12, 2009
So I'm getting annoyed with this ffriend of min that keeps on asking for code off me for a VB assignemnt. Now I'd like to give him some code, but not the right code, (play a joke on him...he...he..). So thats the reason I'd like to write a infinite loop program for Internet Explorer. Would such Visual Basic program be possible?
I'm not going to write anything epic, but probably just the event handler to a button that keeps uploading internet explorer on a infinite loop after clicking. I know morally, this is wrong. I would rather be an ass than a lazy bastard.
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May 9, 2010
I'm not even sure what I need to know. None the less lets say I got a timer with an if event to check if said event is triggered then it fires off some code. The problem is if said event is triggered it keeps firing off the code and I only need to do it one time. Whilst letting the timer keep checking if event happened. I hope I worded that right and here is a rough translation in code. [Code] Is there a way to keep checking if an event happened and only fire off the code one time?
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Jun 12, 2011
I am trying to create a program that the user enters the number of enrollments for 5 different campuses during two semesters. I just got started and here is what I have so far but when I run the program it is stuck in an infinite loop and will not go to the next function. I am not sure how to end the loop.
Here is what I have so far:
Module Module1
Dim SIZE As Integer = 5
Dim campus() As String = {"Decatur Day", "Decatur Evening", "Huntsville Day", "Huntsville
[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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