Stop All Threads Or Just The Thread That The Statement Is Executed In?
Dec 12, 2010
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?
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).
A winforms dialog is using BackgroundWorker to perform some asynchronous operations with significant success. On occasion, the async process being run by the background worker will need to raise events to the winforms app for user response (a message that asks the user if they wish to cancel), the response of which captured in an CancelEventArgs type of the event.
Being an implementation of threading, I would have expected the RaiseEvent of the worker to fire, and then the worker would continue, hence requiring me to pause the worker until the response is received. Instead however, the worker is held to wait for the code executed by the raise event to complete.
It seems like method I am calling via the event call is actually on the worker thread used by the background worker, and I am surprised, since I expected to see it on the Main Thread which is where the mainform is running. Also surprisingly, there are no cross thread exceptions thrown.
I've seen this in two different places & can't quite figure it out. I can think of at least two possibilities but don't have a lot of confidence in either.When stepping thru code I encounter the following:
If x = True Then y = New ContextMenu Me.ContextMenu = y
[code]....
x is False. The debugger stops on the If & I press F11 to evaluate it. The Debugger then advances to Me.y.MenuItems.Add(z), which is *not* the next statement that should execute. Nor does it appear as if it does execute as, when I press F11 again, the Debugger exits the Sub, as it should. But why highlight it as if it will execute?This is even more confusing in the next example:
If Not Me.FindForm Is Nothing Then If Not TypeOf Me Is A AndAlso Not TypeOf Me Is B Then Me.x = "OFF" End If
[code]....
Me.FindForm is a Form, so it's not Nothing. Me is type A so the 2nd If is False. The Debugger stops on the 1st If, I press F11 & it advances to the 2nd If, as it should. Then I press F11 again & it advances to FatalException in the Catch block. What? Did the attempt to evaluate the TypeOf Me cause an error? It shouldn't, and it doesn't seem as if it did as F11 again exits the Sub rather than stepping into FatalException. So why did it stop there?
My first thought was that the intermediate code got out of step with the displayed source code. I've seen that in other IDE's with interactive debuggers, but usually because those allow you to run the Debugger without re-compiling the code. Not so with VS-so that seems unlikely.My second thought is that it's stopping there because those are the last 'executable' statements in the Sub. But that doesn't really make sense as, in other Subs, it will stop on the End Sub.
How do i find the record pointer AFTER the select statement was executed. I am excuting the following code, but i need to move my pointer to the found record
adp3 = New OleDbDataAdapter("SELECT * FROM Recipe1 where RecipeName = '" & RecipeName & "' ", con) adp3.Fill(dt2) ListBox1.Items.Add("RECIPE NAME : " & (CStr(dt2.Rows(0)(UCase("RecipeName")))))
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.
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 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.
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.
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 have the following Stored Procedures create or replace PROCEDURE WEB_AC
[Code]...
First one: At some point in the application I have the valor parameter (of the visual Basic Function) as a string with spaces that is something like "some string with spaces". When this happens, the stored procedure don't update the table. If I execute the SP directly in the DB (with SQL Developer) all works fine. I know it has something to do with the string missing some quotes(') but I haven't make it work yet. Some ideas on this?
Second problem: Sometimes, when debuging the application, if I interrupt the execution, I start getting the ORA-24338 'statement handle not executed' error for hours every time I try to execute it again. I believe it has something to do with an open transaction. But honestly, as I'm new in working with Oracle, I really have no idea what the problem could be.
I'm having a hard time stopping a thread. Whenever i close my main form the application doesn't stop because there is a thread still running. I tried every solution I can find in the web but i can't make it work.[code]...
I have the following code running in a thread to enumerate the local machines in the active directory. This takes some time to complete (about 5-10 seconds) so if the user quits the application before the enum is complete the application takes 5-10 seconds to quit. I tried thread.abort but because it is waiting for For Each SubChildEntry In SubParentEntry.Children to complete it doesn't abort until this returns.
Dim childEntry As DirectoryEntry = Nothing Dim ParentEntry As New DirectoryEntry ParentEntry.Path = "WinNT:"
I have an application in which there is a do...loop. I need the do...loop to perform some code and then stop for .1 of a second. When i try using System.Threading.Thread.sleep(), a wait cursot comes up and the application stops working. I was wondering if there was any way to get the thread to stop without stopping the application.
I have a VB .Net service, which uses System.Threading instead of a timer to basically do what a timer should do. My problem is stopping the service while the thread is in its sleep state. See the code below:
Imports System.Threading
Public Class AService Private stopping As Boolean[code].....
If say 1 minutes after the service starts, it can not be stopped until its 15 minute interval ticks and the thread wakes. Is there any way to catch the signal that the service is attempting to stop, and interrupt the thread?
I'm currently making a bot that points and clicks. It works great! The only problem I have is stopping the bot.How could I make a shortcut key that stops the bot while it's running?
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?
I have a vb.net application that uses threads to asynchronously process some tasks in a "Scheduled Task" (console application).We are limiting this app to run 10 threads at once, like so:
(pseudo-code)
- create a generic list of 10 threads
- spawn off the threadproc for each one
- do a thread.join statement for each thread to wait for the longest running one to complete.
What i am finding is that if the code called by the threadproc contains any "Debug.Writeline" or "Trace.Traceinformation" statements, the thread hangs. I can see the thread in the Debug - Windows - Threads window, and switch to it, but it highlights the debug.writeline statement and never gets past it. is there something special about the Debug or Trace statements that make them non-thread-safe? Any idea why this would hang things up? If I leave the debug statement in, the thread never completes. If I take the debug statement out, the thread completes in less than 5 seconds.
Say I have a code with 3 methods that do some pretty intensive work. Would executing these methods on 3 seperate threads be faster then executing them one after the other on a single core cpu? And what if it's a dual core or HT?
