VS 2008 Do Something On Each Item In Listbox And Multi Thread
Sep 18, 2011
this is going to be hard to explain but ill try. Question 1. Ok i have a list box with a few items, What i want for this example is to click a button and it will start on the first item and do: MsgBox ("this is item blah blah blah") then after that it will go to the next item and do the same and then the next and so on untill all have been done. The "blah blah" should be the item so if item was to say "hello" then the msgbox would say "this item is hello" I know this would be a lot of msgboxes to close, like if 50 items then thats 50 msgboxes to close, this is just for the example.
Question 2. Ok this is where ive tryed to learn but find it really hard (multithreading) Im wanting all to be multithreaded so all work at the same time, ive tryed a few times but the only way i see it is having a **** load of subs, like if i want it to use 10 threads then ill have to add the same code 10 times or somet, im not sure.
i have attempted all this and failed big time as my way was to get the first item and use that then remove it from the listbox BUT... with it being quite fast the 2nd 1 and 3rd 1 used the same item befor it was removed and to be honest i dont really want them removed. so my attempts took like 2-3 days that was a waste of time really. I Know this is a lot to ask but im in real need of it and these 2 things have driven me half mad.
I've been trying to add to a listbox item from a different thread (thread 2) than the thread in which the form/listbox was created (thread 1).
When I check ListBoxItem.InvokeRequired from within thread 2 it is always false when ApartmentState.STA is set. When set to MTA I get an error. Thread 2 is a unique thread with different ID from thread 1.
What is frustrating is that at one point it was working fine, and then I changed some of the structure of the project and it has now stopped working (and I don't know which change caused this! It was a while ago).
This code is within a form class:
Option Strict Off Option Explicit On Imports System.Threading Friend Class MainWinForm
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?
I am trying to get diffrent backround colors on the items added to the listbox (And no, i cant use ListView becouse it misses some important stuff..)I have found some code, but it only changes the text..
I'm working with VB 2008 and I have a problem when using multiple listbox. For instance, I have 3 listboxs (StudentID, Surname, GivenName) and all of them are related to each other. I would like to allow users to remove a specific item by typing StudentID. Then StudentID, and two related data Surname and GivenName will be deleted also.
I'm trying to add items to a listbox from another thread, but am not getting any. [Code] I've verified that inside the FOR loop, in the UpdateUI method, DOES have the correct values, they just aren't being added. What am I doing wrong here?
I have an application which is working. Basically you put in the PC name/ip and it returns the logged on user. I am happy with this part. There is also an option where the program can read a text file of PC's. It will then create another text file with the name of the logged on user next to each pc. This part works, however the program is non-responsive during this time (there is a progress bar, so you can tell it hasn't stalled). I would like to multi-thread this part of the app if possible, Just starting the related sub procedure as a different thread would be a great start - I'd like to start a new thread for each pc in the list to be scanned (if this is recommended) however I imagine this might be slighly complicated...The part I'm referring to is the Sub Procedure "ReadFile". This then calls the Sub Procedure "CompareUserList".
I am creating an IDE for a game script with similar functionality as the Visual Studio IDE (at least, some of it). The game script consist of code that looks visually a bit like C code. It uses braces to define the start and end of a 'class' and uses nested braces to define the start and end of an 'event' in a class.
What I want finally is to have two Comboboxes above the text editor, one that lists each Class and the other listing each Event. The comboboxes should also show the Class and Event that the caret is currently in, just like in Visual Studio.I have attached an example of such a script (you can open it with Notepad).However, here is a short example where you can also see how I "defined" classes and events:
class1 { event1 {
[code]....
As you can see, the classes are the 'names' of each block of code, defined by matching braces { }. The events are the names of each nested block of code, also defined by matching braces { } but inside a class. There is only one level of nesting.As you can also see, the layout can follow the standard C-style layout, or a slightly different layout (using the opening brace on the same line as the class/event name), or even a completely chaotic mess. As long as the braces match correctly, the code is valid.So in short, the large blocks are classes, while the nested blocks are events.
What I want to do, is parse an entire script, and store all the Classes (and eventually, also all the Events, but let's forget about them for now). I want to store the Class name, start position (defined as the start index of the name), end position (defined as the index of the closing brace) and the full text (defined as the text between start and end position, so including the name).
vb.net Public Class clsClass Private _Name As String
[code]....
The code works basically by finding every first opening brace (the opening brace of each CLASS, not event), and then loops through the class (using a brace counter to keep track of the nested braces) until it found the last closing brace. It then stores the name, start, end and fulltext in a new clsClass and adds it to the list to return.
As we know, one STA UI thread creats the controls only canbe accessed in the UI thread in Winform application. And we need to call control.invoke or begininvoke to run the code in the background thread.
Yes, below code in VB.Net , VS 2010 Winform project can throw the exception "Cross-thread operation not valid: Control 'Form1' accessed from a thread other than the thread it was created on."
It is my previous problem in vb6, its hard to multithread using vb6 so I migrate my codes to vb.Net.How can I multithread this two loops so that this process is running at the same time.Because when I start my second Loop, my first loop stop in executing. It will start again when my 2nd loop finished.
[code]...
I have 2 connected GSM Modem in usb port.That codes will send SMS in all contacts in my ListBox.
problem that i am facing is i want to add array of object as a single item in listbox. in vb6 i was using this Label1.Caption = Label1.Caption & Mid$ (strInput, intI, 1) & " " List1.AddItem (Label1.Caption) i was using label. caption to store object but not work in vs2008 because label.text only take text and left other values
I have 2 listboxes on my form.Listbox 1 - populated with "available" field namesListbox 2 - populated with "selected" field names.There cannot be the same field name in both listboxes - it's either one of the other.The logic I was going to apply was to populate Listbox 1 with every field name ... and then as I populated Listbox with the field names which the user has already selected, remove the corresponding item from Listbox 1.
In my application I have a listbox and SelectionMode should be MultiSimple because users need to see which items they selected. In another tab we have another listbox this one should show all the selection users had done in first tab. Private Sub
At first i was gonna use a foldertree with checkbox's but ive decided thats a bit beyond my skill level so ive decided to go with a listbox.now i have a listbox and ive added some lines to it, basically just C: and D: now i wanna use them lines in the listbox in the following command.vb My.Computer.FileSystem.CopyDirectory("C:SourceDirectory", "D:DestinationDirectory") so i wanna run that command for each item in the listbox and use the text in the listbox as the source, and eventually ill try add a
I'm experiencing an error which complexity and way to approach I can't quite understand.. It looks like two threads not able to work simultaneously.The first thread is the normal program thread, and the problem occurs when the user clicks a button. This sends some messages through a method (PlaceOrder) of an API library object. This method is called 2-3 times in a loop. Handlers have also been added (on program startup) to receive callbacks on events raised by that object, and this is the 2nd thread that contributes to the error.
The error seems to occur when the PlaceOrder method is called while receiving an event from this same object.The result is that the UI freezes. I can trace the error in two places. If I trace the first thread (which is the initial program thread); the freeze occurs when reaching the lock(this) line, in the API-object class. If I trace the callback event, the handlers of this event try to invoke a RichTextBox on the form, and the freeze occurs on the line <RichTextBox>.Invoke(....), as indicated below.
The thing is that when pushing the button, there is a loop which calls the method of the API-object 2-3 times. And the first time succeeds, but the 2nd time it seems to crash in some way with the callback. It would be nice if I had made some silly mistake with the invoke code, but I don't think I have, as it updates fine prior to the error.. I'm not sure, but it may be relevant that it's in fact the same object, so early in my program I add this event listener (which is the one that updates the RichTextBox):
AddHandler ibclient.Error, New EventHandler(Of ErrorEventArgs)(AddressOf client_Error) ..while later, related to the freeze, I have:
ibClient.PlaceOrder(....)
But I'm handling a lot of calls forth and back other than these, and haven't experienced any problem before.it doesn't give any exception or error message, it just freezes.The invoke stuff in the form code, which should be as per trusted examples: (Freeze occurs at blue highlight)
Private Delegate Sub SetRichTextBoxInvoker(ByVal message As String) Private Sub OnLogUpdate(ByVal message As String) If Me.rtbTwsMessages.InvokeRequired Then[code]........
How do i go about multi-threading that, it's just an example project, so i can try and learn from it. As i'm having a hard time understanding JMC's tutorial as it doesn't directly relate to what i'm trying to do [code]When you hit 'Start', the start button is disabled and the Label1 then changes to "Downloading".The data is then downloaded and put into the Textbox1.Label then reads "Complete" Start button is enabled.
i know that a single function could not be run until it has finished and is currently not running. what if i have 2 functions within a class, are both of them allowed to run simultaneously? or will running 1 of them prevent both of them from running until it is done?(assume that backgroundworkers and threads are running the functions of this class)
EDIT: plus what if a single function has multiple signatures, is it considered a single function or 2 different functions? could both of them be running at the same time or only 1 is allowed to run between the 2 at any one time?
this is my first post and my knowledge of Visual Basic is still in its infancy (this is my first real attempt at app that is any use) however I am trying to develop an application to delete user profile and home directory folders.
I have the application working but the problem is with the application hanging (I understand this to be due to it running as a single thread and the main form gets ignored while the deletion is occuring) during the deletion process, I have tried various ways to resolve this such as starting the delete procedure as a new thread but cant get it to work without the hang.
i want to process a list of strings using multiple threads. the first function pases it, it then send the result to another, and finally that one displays the final result in list view
dim items as new list(of string) private sub button_click() start parsing thread threadParse = New Thread(New ThreadStart(AddressOf startprocess)) threadParse.Start()
In the event of SelectedIndexChanged() I need to updated text of an item that is highlighted. If I remove it and .SetSelected again, this event will be entered repeatly. So how to update the text of this item in this event without deselecting and re-selecting it?
