Multithreading Efficiency (Reuse Background Worker Subs / Functions?)
Oct 3, 2011
I have an application that queries DHCP and pulls scope/subnet information. There are roughly 8k scopes on our network to query so reporting this data takes a little bit of time. I currently have this running on it's own thread and reporting to a progress bar so the applications doesn't seem inactive.
The DHCP api functions can report a total, a max read and a resume argument. This means that I can, in theory start 4 threads and have each thread read through 2k subnets, so it will only take 1/4 of the time to read all this data. Would I need to create four separate background worker handlers, do_works, runworkcomplete, report progress etc.?
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May 3, 2012
I am using query from a SQLite database as the AutocompleteCustomSource for a ComboBox. Also, I want to load data in separate thread. My LoadData method works fine when called directly, but it fails when it is called from the BackgroundWorker thread. When it is called from the background thread, it throws a Specified cast is not valid exception on the csearch.AutoCompleteCustomSource.Add(hh("Taj")) line. Below is my code:
Sub LoadData()
Dim connetionString As String
Dim cnn As SQLiteConnection
[Code].....
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Apr 14, 2011
I have created a background worker using a tutorial. I understand some basic stuff like how to update a label or a progress bar from inside of it. The purpose of this background worker is setup a bunch of variables that are going to be used by several other background workers later. The variables i am setting up are 6 different lists and a multi-dimensional array. The code looks like this for the background worker at the moment.
Private Sub My_BgWorker_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles My_BgWorker.DoWork
For i As Integer = 0 To m_CountTo
[code]....
I would normally use the persons.add to add something to the list, but I'm having a really hard time wrapping my brain around an easy way inside of the backgroundworker to add new values to several different lists(which are going to vary in amount of data values). Is there an easy way to do this? I'm used to just having invokes at the top of a sub to do this but those don't seem to work inside of a dowork sub.
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Jul 8, 2010
Im using Vb.net visual studio 2008. i have got a process(system.diagnostics.process) to be run in background and it updates the Ui thread progressbar and a label and i have worked it using backgroundworker.runworkerAsync. Now the problem is i have to work the same process for a number of time with different inputs.
The code block is :
Private Sub fnStartEvent(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStart.click
Dim inputFolder = Directory.GetFiles(textboxSourceFolder.text)
Dim currentNumberOfFile As Integer=1
[code]....
The problem in here is the fnStartEvent method once gets started, it calls BackgroundWorker1.runWorkerAsync process and that runs in a seperate thread and does not wait for the thread to complete and it moves to the next line of code i.e loops to the next item and it returns to same BackgroundWorker1.runWorkerAsync line and throws exception that it is already running.
Tried
1.
Private Sub fnStartEvent(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStart.click
Dim inputFolder = Directory.GetFiles(textboxSourceFolder.text)
Dim currentNumberOfFile As Integer=1
[code]....
But this does not updates the Ui thread used to denote progress.
2.Put the whole process inside the DoWork thread and loop for each file in there itself, but that to returns the cross thread error in progress bar updation.what is the standard procedure in executing a loop for the backgroundworker to wait for finishing as well as update the UI without blocking it.
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Mar 28, 2012
I have a DataGridView that I'd like to load with data that I'm retrieving from a SQLDataReader running in a background worker as the data comes in (it's a query that takes a long time). My goal is for the user experience to be similar to searching for a file in Windows where the results appear in the list as they come in and you can still interact with the window.
I have it working with a background worker and data reader and I'm trying to add the row from the SQLDataReader.Read through using the BackgroundWorker.ReportProgress method. Everything technically works but the flicker is crazy and the form is unusable (probably not because the GUI thread is blocked but just because there's so much going on...) How do I make loading the datagridview "smooth"?
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Oct 26, 2009
When you refrence a Function like this one:[code]You may want to be able to get more out of that, like this.[code]So how would I be able to add subs or functions onto a sub or function like that?
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Mar 11, 2009
I have the following code that adds a background worker into a VB.net WPF project:
Imports System
Imports System.ComponentModel
Imports System.ComponentModel.BackgroundWorker
[Code].....
And I get the following error for the DoWork worker event:
Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
It seems like it's missing something in the Event declaration, but can't find it.
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Apr 23, 2012
Public Shared _formRef As frmMain
Public Shared f As frmMain
Class Server[code].....
but once firing off the code i get the error you see in my image attached.
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Feb 21, 2010
I was reading the lesson on how to use functions and subs and I'm having a bit of a hard time understanding this part:
[Code]...
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Jun 14, 2009
I don't mean to sound unintelligent, but is there a way to insert your functions and subs into visual basic and call them from and program made in visual basic? I don't want to have to put the code in over and over again.
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May 21, 2009
I was wondering how to implement a vb script file with functions and subs that can be used in all code pages of a project. Similar to the old VB 6 bas files.
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Apr 7, 2009
Option Explicit On
Option Strict On
Public Class frmMain
Private Sub btnSub_Click(ByVal sender As Object, _
ByVal e As EventArgs) Handles btnSub.Click
Call CalcSumSub(CLng(txtN.Text))
[Code] .....
I'm not receiving any errors or any thing I just need figuring out the logic in this program. The Program Needs to Accept Input in One text box and adds n numbers together and displays the sum using only subroutines and Functions.
Attached File(s)
Assignment5.txt (4.49K)
Number of downloads: 84
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Jun 2, 2011
Earlier I was working on a project, and I added a StatusToolStrip and the the ToolStrip I added a label and a progress bar. The label will say the current sub or function that is in progress and the progress bar will show how far along it is through the sub or function. I have tried this myself but I cannot figure it out as I rarely use progress bars.
An example of a code that I would like the progress bar to show would be like this:
Private Sub StopServer_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles StopServer.Click
'Checks to give server notice
If My.Settings.warningmessages = True Then
Dim cmd As String = My.Settings.warningmessagetext(2)
[Code] .....
So while the sub is running the label would say "Stopping Server" and the progress bar would show how far along the sub is.
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Oct 4, 2008
This is very basic about the layout of classes, subs etc. 1. Should all my subs & functions always be inside a class? I haven't used classes too much before, mostly just a bunch of subs in a form file. Now I downloaded a sample program which I want to develop. This has all the code of the form inside "Public Class Form1": [Code] The code is an example of use of the ZedGraph library. It produce a simple window with one graph/chart. Now I want to develop this code with several tabs, a dusin different charts, file I/O and so on. I'm ok with most of the specific coding, but my question is on the general coding;
2. Should I continue my subs&functions inside this form? inside this class? inside a new class? Earlier when I've NOT been using class, I can make global variables by placing the "Dim" outside the subs. This does not seem to work within a class. 3. Should I avoid global variables all together, or how is this done without always passing arguments?
Also I will make more forms, for program options etc. 4. Should these forms be coded as classes? or just subs&functions in a form? Obviously I'm not well trained on the proper use of classes and have trouble to find this easily explained.
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Apr 15, 2010
I'm trying to create a .dll in VB Express with multiple functions and subs.
For the .dll program, I create a class module with:
Public Class Class1
Public Function ReturnOne(ByRef MyVar As Integer) As Integer
[Code]....
Upon execution, it tells me that it cannot find the entry point in the .dll.
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Oct 21, 2011
At the head of a module, I wish to declare some global variables for use in various subs/functions.
What is the difference between.Dim x as string and Private x as string / Public x as string, and when would I use one over the other?
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Mar 4, 2009
When I code in PHP I usually keep my functions in a separate file functions.php, I am going to write a small function in VB, is it ok to keep all my functions and subs in the 1 file linke in PHP? will they be available in all my form code?
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Feb 1, 2011
I am porting an app from VB6 and I run into problems with references to functions and subs. Basically, let's say I have 2 classes added to the project, like this.
Public Class OOOOO
Public Shared Sub BBBBBBB(ByVal FileName As String)
...
Call CCCCCC()
Call DDDDDD()
etc.
...
End Sub
[Code] .....
I had to make the BBBB() shared to be able to call it from another function AAAAAA() from another class PPPPP. However, I get error on the references in the BBBBB(), that CCCC() and DDDD() have to be made also shared (so instead of 1 error I got number of errors).
When I tried to make them shared as well, I got tens and tens of errors due to other references of both variables and functions.
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Oct 30, 2011
How do I pass parameters of LINQ DataTables through Functions and Subs
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Dec 28, 2011
I have a number of unrelated subs and functions that do various things on my server (e.g. Lighting control, data caching, server maintenance, etc). They are all in various classes which I have coalesced into a single solution.My goal is to create a single, simple interface which each of these disparate classes can be integrated and called from a command line interface. Instead of hard-coding a longish case statement which parses arguments and passes them to the various subs, I wanted to make a generic class which can be instantiated with a minimum of information and put into a data structure. Ideally, adding a new function would involve:
1.) Providing the function pointer (Delegate). The delegates will have various signatures. This is the crux of the question.
2.) Providing ancillary info such as the command-line callable name, number of arguments, argument types, etc.
I have a 100% working class called "node" which is basically a hierarchical tree of node instances. I can use this to simply organize function calls in related branches. All is working quite well.NodeFunctionDelegate(ByVal args As String) As String.The node takes the arguments passed to it by the command line and sends it as the "args" string as comma-separated. The delegate function then needs to know how to split up these comma-separated values, type them, tryparse them and etc. It then must return some string.It works, but it involves writing a middle-man function stub which can receive the argument string from the node class, do the parsing and type checking, and then call the destination function.My goal is to eliminate this trivial middle-man function. The problem is, I can't figure out how to create a variable-signature delegate for the node class.
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May 30, 2010
I'm almost sure that I've seen this somewhere, but I can't find it anymore. Or maybe I'm imagining it, which would'nt be strange either.
When creating a sub or function and adding parameters used when calling it.
-Is it possible to list the parameters that I can enter when using it somewhere in my code?
E.g.
Public Sub MessageMain(ByVal Message As String, ByVal MessageType As String (List of possible values for MessageType)) Same for example as when you have boolean values in a sub/function. As soon as you use that somewhere in your code intellisense will present you with True/False to select.
I'd like the same for parameters in subs or functions I create and calling them from somewhere in my code. Saves me the trouble of remembering which options are available for those parameters.
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Jul 19, 2009
i have have a few questions about the syntax of the lan.:
1) What is the 'Get' statement and when do you use it?
2) Whats the difference between public, private, protected etc... when declaring functions and subs.
3) When would you use the overrides property?
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Jun 10, 2009
Visual Studio 2008, Standard Edition VB.NET I have only limited experience using the background worker, and all that I've done with it thus far was fairly straightforward and worked fine.
I am now looking to run a process in a background worker which calls various functions and/or subroutines, but of course it generates an error indicating that it's on the main thread (or something like that - I don't recall exactly, but that was the crux of it).
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Feb 3, 2011
Namespace MyClassLib
Public Class MainClass
Public Sub New()
[CODE]...
Is it possible to make it so that the user using the Class Library has to declare a new Instance of MainClass() before using Subs/Functions in Class2 or Class3?
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Jul 15, 2011
I'm writing an application in Visual Basic Express 2008, part of the function being to walk through a folder structure starting from a user specified folder. In my research, I found this thing called a background worker which seemed an appropriate tool to use given the potential size of a target folder structure. I successfully installed the two examples from the library here, and believe I understand the principles involved. Even so, having tried to build this feature into my application, it seems as though it is not working as expected, and, as predicted, debugging a multi-threaded application is a pain in the extremity.
I have this fragment under my "start" button click event -
HomeSource.Enabled = False
HomeCopy.Enabled = False
HomeReport.Enabled = False
[Code].....
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Jul 18, 2010
im thinking just because an app has been sent ton system tray does not mean its a "back ground worker"
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Feb 24, 2012
I've got 4 projects all running very similar multi-threading HTTPListener stuff.I wanted to make these functions common - in some module - but I'm having a hard time getting the AddressOf the "callback" passed in.This was the code in one of the 4 projects
Private Sub StartRequests(ByVal prefixes() As String)
If Not System.Net.HttpListener.IsSupported Then
DisplayInfo( _
[code].....
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Jun 7, 2012
my backgroundworker as I just cant get it to work. Basically I have a backgroundworker which does a few tasks but I'm trying to implement a progress bar and a label. I'm going to set the maximum value of the progress bar to 10 and then have it updating as I move with each task, also I'm thinking of a label with the progress bar which will display the progress ie
[Code]...
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Oct 7, 2009
I'am trying to make app that will show every file in C:[code]Now how can i add progress bar with the background worker.
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Nov 20, 2008
I have a background worker that used to fire its RunworkerCompleted event when its DoWork routine finished querying a database and writing its output to a file. The bg worker was in a class called Query, which was called from another class called Trigger. A new Trigger Class was created for each monitored event. In this class, there was a structure which stored the config of each Trigger. When this event was triggered (set to TRUE) a new query class is created and it is passed the Trigger class. When the database query, file writing was done, the query class and all its rsources were diposed from the RunWorkerCompleted EventRecently I changed the application so that a new trigger class is not created for each monitored event. There is a single instance of the class but new config structure for each event. When a particular event is trigger, jsut the config structure is passed to a new query class and the sma ething is done in the query class. I just noticed now that the RunWorkerCompleted event is not being fired anymore.
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