Pass Objects Between Threads Before Child Thread Completes
Oct 15, 2009
What is the best way to pass objects between threads? I would like to create a new thread that creates a new object : Dim myobject as newobject = new newoject Then in my main thread, I would like to use myobject. Ideally I would like to just assign to a global variable but I don't think that is possible. I think I may have to use some form of delegate function (but I think the child thread would need to complete to use a callback). The new thread will not actually end before I need the object reference in the main thread. How should I go about this?
If I spawn a thread with ThreadPool.QueueUserWorkItem and that thread does not reference the object that is not thread safe, would it compromise that non-thread safe object? By not thread safe object, I mean a third party interface to a programmable logic controller that has no ability to open simultaneous connections or concurrency support.I suppose I just wanted to be sure that by queuing threads in the same class as my reference to that object, I wouldn't somehow be compromising its thread safeness in a way I didn't realize.
My program starts a lengthy background operation in a separate thread, and the main thread makes the ProgressBar start scrolling. My question is, how do I tell the main thread how to know when the background thread has stopped, so it can turn off the ProgressBar?
My understanding is that thread.join will suspend the execution of code on the calling thread until the spawned thread finishes or is aborted...
With that in mind, I tried this:
For i = 1 to 50 threads = New Thread(AddressOf test) threads.IsBackground = True threads.SetApartmentState(ApartmentState.STA)
[CODE]...
However, the rest of the code runs when the loop finishes, not waiting for all the spawned threads to finish. Since the rest of the code needs the threads to finish (otherwise the rest will error).
I have a main thread which is designed to be a batch processor - it spawns a series of 'child' threads from a loop (which can vary in terms of the no of items) - see below
[Code]...
However, each of the 'child' threads could take anywhere from milliseconds to about a minute to process - depending on the complexity of each calculation. There may also be a large number of child threads - e.g 100s. Creating large numbers of child threads is not efficient. I therefore want some way to effectively queue each child thread (and cancel if the process is taking too long to complete). Autoevents seems like one way of doing this, but the only examples I can find seem to assume there are two different processes on seperate threads, not one process being repeated.
I have a nested class, let's call it class1 and it has class2 inside it; VB.Net eg:[code]
1) How can I define X number of Class2 objects[let's call it: Node(x) array]** with NEW() subroutine called?' this raises error: dim cls2(n) as new class2 end sub.
2) How can I return actual number of Node() array? [code]Outside my class in main project I define cls1 object:[code]Now an array of class2 is created inside cls1.
3) Now,How can I access All of them[node(x) array which is created inside cls1] with all properties and methods available?
I remember I wrote a ProcessManager class with this functionality in .net 2003, nearly 4 years age, I don't have the code now.
long story short, I have created a ListView type control, using UserControls for the parent control and the ListViewItems. Most the of the control is written and works fine, right up to the point where I tried to replicate the 'Control.SelectedItems(0).Index' property and the 'SelectedIndexChanged' event.
Each child object knows its index value, and could pass this value via the SelectedIndexChanged event (assuming this is how it works in a normal ListView control -- user clicks on an item, and that item fires an event updating the selected index value in the parent object).
How does the child object raise an event in the parent object? I have a feeling this could be done with Delegates, but I'm still learning about their usage.
I have a dictionary object (let's call it _do) I am using to cache some values for use in a multi-threaded program. I have a single controlling parent thread, with a timer function _doTimer() which can kick off child threads with a new instance of class MyThreadObject in each. My parent thread has _do as a property and with each time _doTimer() gets called, it may or may not repopulate _do depending on cacheflag settings. I pass a reference to _do to each instance of MyThreadObject and those threads at some point read the values of _do but DO NOT write to it.
What I want is to ensure that the child threads do not try and read _do whilst the parent thread is writing to it. Same thing but very slightly different -> I also don't want the parent thread to write to _do whilst the child threads are reading from it. However there is no problem with 1 child thread reading the values of _do at the same time as another child thread is reading the values - so ideally I do not want each child thread to completely lock out read access, only locking out Write access.. The code is roughly like this:
I'm working with BackgroundWorker, I want the BackgroundWorker do the retrieval process of data from database while the user can still do another task on the form. The problem is, after retrieving the data, I can't seem to access the ListView in my Form from the DoWork event of BackgroundWorker, I will populate that ListView using the data I've retrieved.
Consider this example, this is how I'm doing it:
Public Class Test Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
I have only managed to use an STA to run a long running excel process with a background worker and 2 delegates.
What I want to do now is have the whole application running outside of the main thread to make sure the UI is always available, I then want to create new threads from the thread I have outside of the main to run the various processes. I will need to have some form of syncronisation in there for certain things to be done once a thread is completed and also I will need to change the button states on the main form to stop certain process being called whilst other processes are running.
This is my code so far, basically this loads in a csv file to a datatable adding manager employee ID and email address, filters it and displays the resultant data in a listview. There eventually will be some filter options as well. There are then 2 options for processing the data, it will produce individual bradford factor reports and email them to each manager or will produce a summary spreadsheet that is sent to HR.
Currently because there are around 8000 lines of data, it was the summary option that required the background worker as a long running process time out error was occuring whilst in the main.
What it does is write the data from the list view to an excel sheet and colour co-ordinates the summary rows according to the absense policy. It then copied bottom to top, the summary value the next blank column against all the lines for that individual and then uses this column to decide which sheet to move the row to, copying the row to the new sheet then deleting it from the master list and shifting the cells up.
This works well, but the process of loading the data in to the list view locks up the main thread where it currently runs. I also wanted to make this slightly more complicate as far as threading is concerned, as more of a learning curve than a practical application of the function.
threads that watch folders and process files. This works fine, but every time needs change to add a new folder or just change some existing rules I have to go in and change the program. I want to builda front end that storesprocessing infofor each watchfolder. The program would then read the configs and build the threads based on them. I cannot find a way to loop through creating the threads.
In my application I have a loop that makes calls to a website to download data. I'm using a DownloadDataAsynch call with a handler.
I'm making many such calls in a loop. What I'd like to do is, if I have more than a certain number of replies pending, I should pause the loop and let the data handlers run.
I've been reading up on multi-threading and just have a couple trivia questions that are ambiguous given my sources:
1) What is the max number of threads in the thread pool? The number 25 is used but I have on reference that says 25 per CPU and another that says 25 per core. I realize that both can be right but before I start making flagrant design decisions I'd like some validation.
2) Let's say I'm in the body of a delegate and I call a function or sub. Does that function/sub remain in the thread or does it revert to the parent thread? I'm guessing the former would be much easier to implement so that's probably what MS did but you just can never tell.
Does anyone have a 1 to n thread example in which n threads are created dynamically? There are a number of examples that show a definite number of threads, and some that imply n threads by using a tcp ip listener or a file system listener. However, I'm looking for a 1 to n created in response to a dynamic requirements, provided purely by and for my program.Essentially, my requirement is to be scalable. 1 to n threads based on application throughput should make this pretty easy to satisfy.
I'm working with vb.net 3.5SP1 /VS2008. I'm familiar with windows threads from C++ but I didn't do it since the 90s.I have 5 threadpool calls (ThreadPool.QueueUserWorkItem) that do some complex work (they read info from different web pages, regular expressions, etc) and each updates different columns in a data-grid view. They pause for 1 second between each web read with thread.sleep (not to overload the server). My issue is that some of the threads do not complete. I get for example 3 results when I should have 8. Sometimes it works fine. This is an older 3.0Ghz HT machine, I want to test it on the lowest common denominator(and that is all I have ). I tried using Monitor.Enter(ListView1)it seems to help but it is hard to tell. I tried using the thread debug window but it is not really helpful, it seems do disappear during execution. If I remove the threads I always get my data. I'm wondering if something is being blocked? Is there a way to debug this?
Also, does thread.sleep(x) stop all threads or just the thread that the statement is executed in?
I have a thread pool that send file using ftp protocol. I encapsulated the call for threadpoll with try catch believing that the thrown exception inside the threadpool will be catch by the main thread. Instead the system terminate whenever i throw an exception from inside the threadpool. Also I design the Clsftp.ftpsend class to throw an exception related to ftp error. Basically my design for handling the error is just like the code below.
'Main thread Private Sub BttnStartSending_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BttnStartSending.Click try Dim objparam As New ThreadParameter
I have need of either enumerating all the managed threads in a application or listen to when a new thread is created. I can not find anyway to do this through searching the web. It strikes me as odd the the IDE can list all the manage threads, but I can't.
If this is not possible, is there clarification as to why this is not possible.
I need to create a shared class in a DLL that will when it receives a signal will stop all the threads currently running, and gracefully exit the application.
I just made a rapid file transfer form for my photos.In which I drag photos into a listview with my destination folder set.I assign each individual file transfer to a new thread. This works very fast as compared to the standard drag n' drop.
I am creating a tool that interfaces with an API for a CD/DVD burner. I have created several custom classes that will hold the information for the disk sets (which consist of a data path and a label file among other information. The DiskSet class has a list of Include objects. My proposed XML output would be something similar to the following:
<DiskSets> <DiskSet> <Name>MySet 1</Name>
[code].....
I am attempting to traverse the Includes collection (I have tried List and Binding List as I am also using this in a pair of datagridview controls) and it keeps returning Expression of type 'Object is not queryable. Make sure you are not missing an assembly reference and/or namespace import for the LINQ provider." How can I use LINQ to pull a list of the Include objects under each DiskSet object for transformation into XML? I am hoping to keep this restricted to this one block of code if possible.
I have a program which has a rather complicated component within it. This component has a number of features that all run at once and will cause lag with the main application which isn't acceptable.
To resolve this issue I'd like to run these processes on the component in another thread. I've created a simple test version to work out how I'm going to do this, however I've run into a few problems.[code]...
Is there any issues with this? If I'm kicking off half a dozen threads over and over? ie: I'm not using a system where the parameters will get mixed up/corrupted?
I've looked around, and if this is OK/safe to use, this seems the easiest way to get values/params into a thread.
I'm trying to pass a list of objects to my WCF service, but it doesn't seem I can pass an object list from my console test application. I have an error that states:
Value of type 'System.Collections.Generic.List(Of ConsoleTestingApp.ServiceReference1.LetterVariables)'
I have an object of type Dictionary(Of Int16, Polygon) and which contains sometimes up to 15 or so Polygons that i am creating bitmap files with the Polygon. This can take like 20 seconds sometimes so i was trying to pass the full Dictionary to background worker as an argument but i get an issue when trying to access each individual Polygon inside of the Dictionary because the Polygons still belong to the UI thread. How can I access the Polygons inside the Dictionary with the backgroundworker?
Dim worker As New BackgroundWorker AddHandler worker.DoWork, AddressOf MeasurePolygons AddHandler worker.RunWorkerCompleted, AddressOf WorkerCompleted worker.RunWorkerAsync(PolygonCollection)
that is how im calling the thread. PolygonCollection is the Dictionary(Of Int16, Polygon) that contains all the polygons that i will be creating a bitmap file out of.
I am finding that this may not be possible, but am trying to see if anybody has a solution.
I have four classes, two are core classes and two are those core classes extended[code]...
This fails because es is of type, extSecurity and the base class expects a type of coreSecurity. I've not found anyway to cast this to allow for me to override this base class in C#. In VB it works just fine.
now the form customer master has values within a listview. when i doubleclick on a value within the listview i want this form to close and pass the value to a textbox within the parent form. what would the code be? I am relatively new to vb.
