Threading From For Each Loop
Mar 21, 2012
I have an app that the user selects a database and the user tables are displayed in a listbox. The user selects which tables to export to an Excel workbook, one for each table. There is a richtextbox that informs the user when the created files are done.
The app works and the xlsx file are created as expected. The problem is when each is finished only the last file of the selected tables is displayed in the RTB.
The form has the following Handler
[code....]
The threading is done in the following
[code...]
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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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Oct 17, 2009
When it comes to threading. I've managed to adapt one of JMcIllhinney's backgroundworker codebank examples to somewhat suit my needs, but not completely. I have a main form, and a second form that appears while I'm running through a for loop. It informs the user what is currently happening. I set up a backgroundworker that allowed me to continue to use the main form during the for loop, but the other "status" form was completely frozen, and any labels or graphics were shown as white boxes. I am struggling to figure out how to be able to move/interact with both forms while the loop is running.
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Mar 14, 2011
Makes the following statement about the code below:
**"The computer evaluates the loop condition in the Do...Loop statment to determine whether the loop instructions should be processed. In this case, the inputsales <> String.Empty condition compares the contenst of the input sales variable to the String.Empty value. As you know the String.Empty value represents a zero length, or empty, string if the inputsales variable is empty, the loop condition evaluates to True and the computer process the loop instructions. *If on the other hand the inputsales variable is not empty, the loop condition evaluates to false and the computer skips over the loop instructions.
Based on the code I think it is the opposite: ...that while the inputsales value is not empty it should evaluate to true and process the loop and if it is empty it should evaluate to false and skip the loop?
See below.
Option Explicit On
Option Strict On
Imports System.Globalization
[CODE]...
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Mar 9, 2011
I know I am missing the obvious. I would like a label to show how many cycles in loop are left.
[Code]...
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Nov 23, 2011
I am constructing a program, i am new to Visual Basic, but i have past programming experience. I was wondering if anyone knew how to form a loop that could...lets say calculate the answer when two numbers are added together,and it would repeat this thousands of times, etc. And if there is a way, would it be possible to calculate the time taken to complete this loop.
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May 3, 2010
I have written a function that gets the alexa ranking of a given url, now this function works perfectly but I want to loop through a ListView of urls and grab the alexa rank of each item (url) with my function.The code works great if I put a MessageBox in the loop to test that the function is returning a value but when I remove the MessageBox the loop does not work.I need it to loop through adding each result without a MessageBox stop in each loop.
vb
For Each Item In ListView1.Items
Dim result As Integer
result = GetAlexaRank(Item.Text)
[code].....
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May 31, 2010
So I made a simple patform game where the player has to jump quickly while the platforms move to the bottom of the screen, as to not touch the bottom of the screen. But, I need to know how to create a loop to loop the locations of the platform. This means that after twenty or so platforms, the same platforms come up again, so that the player will have an "endless" game. I've declared all the platform's locations relative to the location of the first repeating platform:
[Code]...
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Aug 11, 2009
I assigned an integer as 1, and looped my program using:[code]I can recieve the packets without looping, but once i loop, i receive nothing.
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Mar 17, 2012
I am trying to send emails on a button click ...but I want to send the emails in the background as the number of emails are too many...so I am using threading.
[Code]...
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Sep 1, 2010
I have a program that I would like to implement using Threading.I wand to load a form that takes a couple of minutes to open using threading.Here is my code
Imports System.Threading
Public Class frmAdjustments
Function LaunchForm() As Integer[code].....
I am new to .net programming and could use any suggestions you may have. I'm trying to grasp the concept of multithreading apps and would like to have both my main form (Adjustments) and the (frmNewAdjustments) form to load concurrently.Here is the error I receive with the code above: Overload resolution failed because no accessible 'New' can be called with these arguments:
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Feb 21, 2011
i'm trying to do a database search in my WPF program. And to give the program some speed, I want to use Backgroundworker or Threading. The problem is that i have to invoke the controls that the new thread is going it access. But i don't know to do this and i don't know i which event to put the code. Here is some code:
[Code]...
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Mar 3, 2009
I need to be able to call a C++ dll that takes a long time (possibly infinte, it relies on user input)to execute. Im calling this through VB. My VB GUI freezes up when this happens, and I would like to keep the GUI responsive, so that the user can stop this possibly infinte loop. A bit of background, the C++ is trying to keep score on a snooker table using a webcam, and while the VB scoreboard updates easily, I would like to script it so that the analysis is almost continuous, while still allowing the user to interact. Currently the project requires the user to press a button to start the shot analysis, but it would be preferable if the program scripted itself. I have only realised this problem now and the deadline is very soon.
Update: Our lecturer suggested an option to solve the problem, but it would appear that most options here and the one he suggested will not work for us as the processing time required for the webcam image capture is too great to handle due to hardware constraints.
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Aug 15, 2011
I have the following code. My program loads 20 pictures in one panel and each pictures has for the moment like 500 Kb, but in the future they shall have like 2~6 Mb.When I use this part of code, my program that uses only 6 Mb of memory, but jumpes at 202 Mb when pics are loaded. I need a method to resize or make them thumbnail or something to reduce the memory.I don't know for the moment how to use the System.Threading, but I want to know if it shall help my program, if not, then help me replace parts of my code.Private Sub PanelPictures(ByVal picsoriz As Integer) ' picoriz represents how many pictures should the panel have on each row (it's set at 5 pictures per line/row) [code]
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Jun 8, 2011
I have a program that I would like to implement using Threading. I wand to load a form that takes a couple of minutes to open using threading.
[Code]...
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Jun 26, 2009
SMS Multi Threading
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Nov 16, 2009
I have a VSTO application, rendering a word documement. At each stage of the rendering a popup window is getting displayed. What we have done is displayed a popup window, and at each stage of the rendering the text is made Changed. I need to display the window using multithreading. How to achieve this.
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Feb 23, 2011
I'm trying to understand how to handle db connections in a multi-theaded windows program.It I have this simple class:
public class MyClass
private myConn as new sqlconnection
private MyThreadPool(5) as Thread
[code]....
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Aug 24, 2009
threading in diffirent class?? I get an example like this
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim NewThread As New Thread(AddressOf Counter3)
[code]....
a thread at example above was written in one class, now how to make a same thing like that with a different class?? and one more thing if you click the button twice then it have two proses.
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Sep 23, 2010
how the threading within vb actually works. am i of the understanding that every time you create an event, through a button control for instance, that this infact creates a seperate process which will run independantly to another. say for instance you had two buttons on a form and each contained code which took 5 seconds to execute. if i were to click one button into action and then the other with a second, would the two processes run alongside one another or would i have to wait for the first code to execute before the second button could be executed?
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Jan 23, 2012
I am communicating with a USB-HID device. It will successfully complete hundreds of send-receive requests but occasionally get a Null Exception error.
[Code]...
at the rxData.dataPacket(i) = element I will get a NullReference error every now and then. I could enclose it in a try/catch statement, but I'd like to fix the root problem if possible.This device is communicating to microcontrollers, and it is possible that they won't always give a value... but my feeling is this is some sort of UI threading issue. When debugging, even though there is a null exception, many times there actually does seem to be data in dataReceived.data.ToList(). Is there an easy way to place the whole data processing routine on a thread separate from the UI?Edit: Changed code to match answer and give more info on where it is used. Still get NullReferenceExceptions after about 1,000 completed send/receive requests to the HID device.
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Apr 25, 2012
I have a problem. I'm creating a new thread, which should do some stuff and update a text box. But, when I test my program, the main (UI) thread is doing all the job, even though I declared and started a new thread.
[Code]...
I even made another thread for testing purposes, but it was the same.
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Apr 2, 2010
I'm developing an adding for office powerpoint application.I'm trying to display a description of the object(Customized object) currently dropped on the powerpoint slide in design mode(Design mode of the powerpoint).When i click on my addin the related object description will be displayed on a tabbed window as the first tabpage.
There is a button on the tab page, and when i click on it i need the description to get copied to windows clipboard.I tried this using clipboardclass it throws the following exception, System.Threading.ThreadstateException {"Current thread must be set to single thread apartment (STA) mode before OLE calls can be made. Ensure that your Main function has STAThreadAttribute marked on it."}
Code for clipboard:
Clipboard.Clear()
Clipboard.SetText(lblObjectID.Text)
I searched the net for a solution and got couple of answers like, Put [STAThread] in the main function Thread.CurrentThread.SetApartmentState(ApartmentState.STA) Immediately before your call to SetDataObject.
But I'm not sure where to put the 1st one and the 2nd option didn't work.
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Oct 3, 2010
I'm using vb.net 2005, I've got the following code running a thread to download a file. However, the process fails sometimes when trying to read the local copy of the file. I think I may need to unlock the local file somehow but I'm not sure how to do this.[code]
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May 30, 2009
I know .Net and C# pretty well, but never even looked at VB.My problem is: our Win32 COM library is used by a number of clients, and we see that the number of failures is higher for those who use the library from VB (both VB and VB.NET) than for those who use C++, C# or Delphi. One thing about our library is that it is supposed to be used from one thread only - can some threading magic by VB be the cause of failures?
Clients tell us the do not create any extra threads on their own.
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Feb 15, 2009
I'm creating a password hash recovery tool that uses brute force. I have the brute force algorithm run in a background worker. It all works, but some similar apps I tried out have performance ~100x bigger then my app. (mine does 50k keys/second, some others do 5m keys/second or more.)I realize this is partly caused by using a .Net language, but I suspect there are ways to significantly speed up the brute force. A lot of ppl say I should use multi threading, but how is this done in practice? Splitting up the passwords to check would slow down my app I think.
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Nov 12, 2010
I have a button click event and inside I do a lot of work. While I am doing this work (not from the UI project) I want to send messages to the UI to display to the user.
[Code]...
and inside DoMyWork which is in another assembly i can call SendMessage which writes to the textbox. The messages will only display though when DoMyWork is complete. How can I update TextBox1.Text on the fly without putting DoMyWork on a BackGround thread or do i have to put it on a BackGround thread? I do actually want to block the user from doing anything while DoMyWork is running
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Sep 9, 2009
I know there are many cases when it's best to multi thread an application but when is it best to multi thread a .net web Application?
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Mar 17, 2011
I'm trying to get threading to work in ASP.NET but for some reason it keeps crashing my local server, and simply does not work at all when uploaded online. Here's the code:
[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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