I try to use Multithreading with VB 2005. I added a Listbox to main form and i tried to fill ListBox with 2 threads. When i executed code it told me that this is unsafety operation becasuse of ListBox is created with Main(Form1) form.
Is there anybody who has such simple multithreading example with Mutex or such lock mechanism?
I have 10 threads each using the same sub to do work. This sub is calling a function to save the results. How are the threads accessing the sub? Is each one getting a fresh copy of the sub to do its thing or are they using the same piece of code and need to wait for each other to finish processing? I don't get any hits when searching for such a specific scenario. I am wondering because it is about using sockets (usually lightweight stuff) to retrieve a resource and the cpu is working at 100% all the time. Still it is very fast, 900 internet queries finish in about 3 minutes.
View 4 RepliesI am trying to get a handle on SyncLock and multithreading, but I am having some trouble wrapping my head around exactly how it should be implemented. I have a Public Class Utilities with a many Shared Functions. I want to make sure that each function can only be executed when there are no other concurrent calls to the same function. So If I have 2 functions, A and B in a Public Class Utilities, what is the syntax so that a function "locks" while it is being executed, preventing any subsequent calls until the "locking" thread has completed?
CODE
Public Class Utilities
Public Shared Function A (ByRef i As Integer) As Integer
[CODE].............................
I know I need to wrap the statements of execution in a SyncLock block, but I am unsure of the scope of the parameter used with SyncLock...is it private to the function, class, etc? Can the same object be used to lock both functions if they are independent?
What is multithreading and how do i do it in vb.net?
View 2 RepliesI am using an Application server for calling Oracle Reports and I have a URL to call the report. When the report is called the server converts it into PDF but when report contains large data it takes a lot of time to load. I want to do in asp.net that when I call the report url it opens the PDF file and copies it into the root of my web folder. The next time when I call the URL it opens the PDF file and creates a new PDF on backend for next call. I have made this function to download file
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In which situations we can do the multithreading and deadlock concepts. can give some examples
View 4 RepliesBasically I am making a proxy testing program. A user can supply a list of proxies to test. What i want to be able to do is have them be able to specify how many threads they want to run. Then have the program go through the list testing each one using the amount of threads supplied. Really not sure even where to start on this. Threadpooling?
View 3 RepliesWhat does common data or data that's in a common, look and is treated by multithreading? I'm quite aware that acess to such data would have to be synchronized, but beyond that is it acessible?
"MODERN PROGRAMMING is deficient in elementary ways BECAUSE of problems INTRODUCED by MODERN PROGRAMMING." Me
I have a class with a background worker in it that does some tasks on a separate thread. I want to fire some events from the background worker thread to the 'main thread' of the class, so that when using this class your not obliged to go make invoke calls for every event handler your using.I'm at a loss of how to do this though. When having a similar problem in a form of usercontrol I always use Me.Invoke, but this method is not present in a class inheriting system.object.
View 1 RepliesI have a screen that checks for alerts every 30 seconds by looking up outstanding issues from a database.When there is an alert, an audio file is played depending on the alert.It takes 1-2 seconds to grab this audio file which caused an issue with global screen freezing, so I added multithreading where it plays the sound file. This seemed to work fine.However I am new to multithreading and am not sure if I'm working with it efficiently..I have simply declared the sound-playing function as a thread at the top:[code]I am unsure if starting and aborting the thread is the right way to do it. However if I suspend or make the thread sleep I would have to determine whether it has been run before.
View 18 RepliesI have read many articles on multithreading over the past few days and so far I'm fairly comfortable with how it works. I am now working on my actual application, and have come across a few design issues that I'm hoping somebody has experience with.The basic premise of the application is simple. A database filled with files names and a "converted" field that has a 1 or a 2 in it (1 for unconverted, 2 for converted). The application loops through every record where "converted" = 1, retrieve the file and convert it.
My single threaded application works fine, except its far too slow. Due to the huge amount of rows in the database (4 million+) and the time constraints on the project, I have decided to run as many threads as the hardware can allow to cut down on the timings.So, the dilemma is accessing database records and which threads should grab which record and how.
I have a function in my program that adjust sales for multiple days. Sometimes it needs to adjust up to 3 months and the tasks takes a while so I decided to split up the work between multiple threads. The way I have it working is say I need to adjust 3 months. I have the first thread adjust sales for the 1st month, the second thread adjust sales for the 2nd month and finally a third thread that will adjust sales for the 3rd month. Since all three threads are performing the same tasks except for different date range they use the same procedures. Within those procedures I make a call to the database to extract the sales for the given month. At some point it seems like the threads start to use the same SQL Data Objects because I am receiving the below error."There is already an open DataReader associated with this Command which must be closed first."Below is the first procedure that is ran by each thread up to the line where it errors out.
Private Sub Process_Adjustments(ByRef objAdjustBillCodeThreadParameters As clsAdjustBillCodeThreadParameters)
Dim cmd As SqlClient.SqlCommand
[code]....
So all three threads call this subroutine and the first thread does the data fill with no issues and then sometimes even the second thread does the data fill with no issue but then the third thread crashes and produces the above error. It seems as though the threads are sharing the same SQL Objects when all objects are local to the sub and I always thought each thread had it's own memory to work with. So I thought each thread would call the sub create it's own objects in memory, but that does not seem like what it's doing. I have other multithreading processes in my application that work perfectly fine, this is the first time I am attempting to multithread in this manner where I am using the same procedure within multiple threads.
Just thought of something that I might be doing wrong. The subroutine in question is in the same class where the threads are created. Should the subroutine be in it's own class, and therefore each instantiation of that class?
what is the right way of Multithreading in visual studio 2008.
View 1 RepliesI m making a project in which it check website about there status (Online / Offline) through there status code and when project is in processing it hang's until the whole line of code complete
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I'm using the WIA Aut. Library [URL] , trying to capture photos from 5 digital cameras (Nikon D90) USB-connected to my pc. Now, I partially achieved my goal, what I do is:
- loop through the attached devices, connecting to every camera;
- fotocamera.ExecuteCommand (WIA.CommandID.wiaCommandTakePicture) ;
- other image processing operations...
Everything works fine but... the workflow is camera1 -> connect -> grab pic. => camera 2 -> connect -> grab pic. => camera 3.....
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I'm using the WIA Aut. Library [URL] trying to capture photos from 5 digital cameras (Nikon D90) USB-connected to my pc. Now, I partially achieved my goal, what I do is:
- loop through the attached devices, connecting to every camera;
- fotocamera.ExecuteCommand (WIA.CommandID.wiaCommandTakePicture) ;
- other image processing operations...
Everything works fine but... the workflow is camera1 -> connect -> grab pic. => camera 2 -> connect -> grab pic. => camera 3.....What I'd like is to make them shoot all at the same moment (...why? well, D90 waits around 1 sec. after a shoot... 1sec * 12 cameras * 500 photo sessions.. :'( )I told myself... what's the problem? You can create "shooting-threads" while looping through the device then launch 'em all.Done.It's still in a 'serial' way... :-(((Why? is executeCommand() a synchronized method? If I madly-fast click on two 'grab pictures' button of windows XP WIA dialog it works.. Is there something about .NET multithreading I don't know?
My application will creates an Excel from DB, creating an excel file takes few minutes of time and till that time the user dont want to wait for the excel to complete, he should start working with the application. Once the excel have been completed the appilcation should po-up message saying, 'Report Sucess'. can any one tell me how to do this, whtr background thread will help me in this ?
View 1 RepliesMy question is to add two numbers up using threads or multithreading. Here is what I have:
Module Module1
Sub ThreadA()
Dim I As Integer[code].....
Is there a way I can use this somehow to add two numbers up?
I am looking into using a producerconsumer threading pattern to run through a list of strings that i retrieve from a database and then am going to run powershell commands against. As the powershell commands can be quite intensive i only want to spawn 3 threads at a time and then wait for one thread to finish before doing anymore. I looked into the treadpool but it looks like it is used for more lightweight processing.
View 3 RepliesI want to download some imagefile from a multilinetextbox and right now i m using this code
Multiline textbox contains :
[URL]
Code 1 :
Code:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim ary() As String = TextBox2.Text.Split(Environment.NewLine)
[Code]....
because in both cases it will download file one by one and i want to do my job as fast as possible by sharing the multilinetextbox data among set of thread's but how to do i dunno
Like if i multilinetextbox contain 100 image file link and i want to run 3 thread at a time then these 3 thread will share/Access the multilinetextbox data what will be the my final code ?
I am developing an FTP program which: Watches a folder. If a new file is dropped there then upload it. Tells user if uploading and when complete. All the above works, however I wan to add the items to a listbox that are being uploaded. So if I dropped 3 items there it would look like :
Upload Listbox:
cake.jpg
myExcelFile.xls
woot.docxAnd as each one is done, or new files are added it removes them or adds them.
I tried using que, but with no luck as the program just hangs whilst it uploads. So I had a search and looked into multithreading and I tried to implement it, but I can't get it to work as it gives me some 'delegate signature' related error message as you can't pass in values when trying to use 'AddressOf'.
Here is my code for the The .created sub:
Public Sub FSystemWatcher_Created(ByVal sender As System.Object, ByVal e As System.IO.FileSystemEventArgs) Handles FSystemWatcher.Created
'if any file created add fullpath to the listbox
ChangeLog.Items.Add("Created: " & e.Name)
QueueListBox.Items.Add(e.Name)
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what i did was i use a select statement in opening multiple IE just for testing but the main function is what you put number on a textbox then the number the IE's will open for example i put 100 on textbox then when i click a button then 100 IE's will open so if im going to use select statement when opening 100 IE my code will be crazy... heres my sample code..
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Here is my code: Imports System.Threading Imports System.IO
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In my application, I have a MainWindow with a ToolStripProgressBar and a ToolStripStatusLabel.
This properties:
Property ProgressBarPercantage() As Integer Implements BCSXPSearchTool.Presenter.IMainView.ProgressPercentage
Get
Return Me._progressbarpercentage
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The code above is working. But if I change the sub runproc() to:
Public Sub runproc()
Dim statusToSub As delegateStatusTo = AddressOf statusTo
Dim percToSub As delegatePercTo = AddressOf percTo
' statusToSub.Invoke("Test")
percToSub.Invoke(50)
End Sub
It doesn't work. I get an exception:
InvalidOperationException
I got the text something like:
The access to the control, created by another thread from another thread is not allowed.
I'm using Visual Studio 2008 Express + VB 2.0.
I've got a vb app in .Net 4 that i'm working on. The app fires up dynamic threads to run some jobs. Each thread runs a certain job and within that thread, it performs a infinate loop. It needs to be this way, i can't have the thread and then begin again...
anyway.. i was using threading.thread.sleep in the loop to have the loop pause for a bit before running again. It seems that this is not a good way to go and not recommended. So i thought perhaps i could use a dynamic timer or something else to have the thread wait for say 30 seconds before running again. i was hoping someone could give me some direction and example code.[CODE...]
If i start a BackgroundWorker or 2 then after some time goes by and i've done things on the main thread what happens when from the main thread I call:
Me.Close?
Application.Exit?
End?
Also if I spin of a Thread: (New Thread(addressof ThreadProc)).start - or however it is, does that thread behave the same as a BackgroundWorker in the above scenarios? the real JeZteR My New Blog: [URL]
I'm attempting to write a lock-free version of a call queue I use for message passing. This is not for anything serious, just to learn about threading.I'm relatively sure my code is correct, except if the instructions are re-ordered or done in registers. I know I can use memory barriers to stop re-ordering, but how can I ensure values are written to memory immediately?
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I am running code in a thread upon opening an Excel workbook that takes some time to execute. If I attempt to close the workbook while the thread is still executing, giving me the standard prompt to Save or cancel, my thread is interrupted (not sure if "interrupted" is technically the right term) when I click Cancel. More generally, it seems that UI interactions/updates cause the thread to be interrupted.
Is there a way to either 1) prevent the thread from being halted by a UI update/user interaction, or 2) allow the thread to resume after being interrupted?Nothing fancy about the code:
Private Shared Sub Test()
Dim t As New Thread(AddressOf DoSomethingThatTakesAWhile)
t.Start()
End Sub
According to the answers to another question, the VB user interface cannot be updated if the thread that created it is busy: hence why big computational jobs usually have to go in a background task.Here's what's mystifying then. I have the following code. It's called over in-process COM, like this
client calls showform()
client does loads of work, freezing up its own UI in the process
client finishes work, returns to updating its own UI
At step 2, the VB form is there but frozen - you can't interact with it. At step 3, the VB form becomes usable. But why is this? Surely the thread of execution has returned to the client? If the client is somehow handling events for the form, by what magic did it know what events to handle and where to send them?
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I have some functions in a web application that do a lot of calculations and as a result have high CPU usage which affects the rest of the application when other users are accessing it. I have tried background-worker to no avail , the only thing that seems to work in using another thread and setting the priority to low, can the UI be updated from a worker thread? specifically I am trying to bind a grid to a dataset processed in the worker thread
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