Multithreading - .Net: Does Debug.Writeline Stop Thread Execution
Aug 19, 2009
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.
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Jun 23, 2012
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?
[Code]...
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Jun 10, 2010
What's the difference between Console.WriteLine() vs Debug.WriteLine()?
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Jan 27, 2012
in VS 2008, I started a new VB console project, using default options. I wrote this simple program:
Module Module1
Sub Main() Dim ArrayOfInts() As Integer
ArrayOfInts = New Integer() {1, 2, 3, 4, 5, 6, 7, 8, 9}
[Code].....
However, I cannot find the output from the calls to writeline. Not in the Output window, not in the Immediate window and not in the console output.
Or, do I need to do something extra to get these to appear?
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Aug 31, 2011
Simple question that does not seem to be covered: If I use a lot of Debug.WriteLine statements in my code, will they be completely absent in my production version?
I mean: Is the compiler smart enough to not emit any code for those calls? Or would I have to surround them by #if DEBUG..#end if directives?
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Sep 2, 2010
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).
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Sep 2, 2009
In the past, perhaps versions of Visual Studio prior to the 2008 that I am using now, I would do something like this in my VB.NET code:System.Diagnostics.Debug.WriteLine("Message")
and the output would go to the output window.Now it doesn't. Something must first apparently be enabled.
If this involves "attaching a debugger", please explain how to do it. It seems to me that it should just work without too much of a fuss.Here's a video explaining the issue in real time and showing you all my settings[URL]..
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Aug 19, 2009
If I have Debug.WriteLine method in my code, do I need to comment all these methods before producing the Release version? Or does the compiler just ignore them?
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Oct 6, 2011
I have a fellow employee who is learning Visual Basic and in one of her assignments she is using the debug.writeline statement. Example: Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Debug.WriteLine("This line always prints") End Sub When you run the program, nothing prints to the Output window. I have tried it in VS2008 and VS2010. Brian Allison
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Sep 28, 2011
I have a procedure that loops through the directories/subdirectories on a file server and sets the permissions. Procedure is called on a button click of a form.
I need to display on the form which directory is being processed. Similar to if we use the Debug.writeline which writes to the output in Visual Studio. I tried using a ListBox but it only displays the last one and only displays the last one once processing is done. I want to be able to display each directory name as it is being processed.
Psuedo code as follows:
For each dir in L drive
setPermissions(dir)
'display in ListBox dir name
lstProgress.Items.Add(dir.Name)
Next
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Jul 29, 2011
Dim hex = "41"
Dim text As New System.Text.StringBuilder
For i As Integer = 0 To hex.Length - 2 Step 2
text.Append(Chr(Convert.ToByte(hex.Substring(i, 2), 16)))
[code].....
but yet this fails.. (the output isn't itself in a new line) what's the explanation for that?From what I know, doesn't System.Diagnostics.Debug.Writeline does something which looks like this:
System.Diagnostics.Debug.Write(input)
System.Diagnostics.Debug.Write("
")
so regardless of my input it should always have a newline char even if there is a terminating 00 char in my input?
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Mar 16, 2012
I am trying to write some messages to a text file using debug.writeline("Message"). Here is the code.
Dim Tr As TextWriterTraceListener
Tr = New TextWriterTraceListener(System.IO.File.CreateText("Output1.txt"))
'Tr = New TextWriterTraceListener(System.Console.Out)
Debug.Listeners.Add(Tr)
Debug.WriteLine("Test Message")
I see the output1.txt file being created but nothing being written in the file.
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Nov 28, 2011
It worked fine till i applicated some conditions... Now my form execution stop right after a ExecuteScalar.[code]
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Feb 6, 2012
How can I completely stop code execution?
Also, how can I hide a form and keep all information saved so I can bring it back up again?
For instance, I have form1 with "alpha" written in a textbox. Now when I hide form1 (Me.Hide), I would like to be able to bring form1 back with "alpha" still written in the textbox.
Currently, I hide it, and when I show it again, the textbox is empty.
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May 11, 2012
I need to stop the execution of a program in VB.net. Within a repeating structure the program checks whether a variable is true or false. When the variable is false I need to stop the program execution. I do not want to close the program but simply stop it. One way I found was raising an exception, but I would not want to display the error message to the user. What is the best way to do it ?
Do
If myvariable=false then
throw new exception... 'Silent exception
end if
Loop until ....
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Dec 31, 2010
I want to stop the execution of my .net application for about 20nanoseconds
so i am trying to measure time needed for specific samples of code, and i want a code that takes only 20nanoseconds
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Sep 14, 2009
my application has integrated an external library with long running math-evaluations. It happens that some calls to functions in this library start but do never come to an end.
Unfortunately I have no chance to look examine the behaviour of the library. So I got the idea to stop my function calls to the library after a timeout.
Has anybody an idea how to manage this an to control the execution of a function, i.e. to stop it hardly after a certain time?
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Aug 19, 2009
Is there a command that will stop the execution of my program?
I have a service that is processes an exchange account via telnet every 10 minutes. During one point of execution the application could possibly have a response from the telnet session when there are NO e-mails in the folder, which would look something like this[code]...
So is it possible for me to just stop my application at that point since there's no point in continuing if there are no e-mails in the account?
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Jun 15, 2011
I have written a converting program, which converts binary files to ASCII files. (VB.net 2010). I need to have a functional "stop" button on the form and I was wondering if there was a simple command to make a program stop, exit all procedures, and wait for user input on the form.
It is not feasible to multithread this application, as it frequently interfaces with the form. Currently, I have a global boolean variable which becomes true if the stop button is pressed, and I have internal loops checking to see if the variable is true. However, I don't to waste CPU on checking a variable if it's not necessary.
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Nov 24, 2009
I am checking to see if a textbox contains a number, or is null. If it is non numeric or null a message box appears asking the user to input the proper value. When the user clicks OK on the msgbox the program will continue to execute the code. I want it to stop executing the code and revert back to its default state as it would be if you just opened the program. What is the command for doing this so I can add to the if statement?
Dim numCheckV as boolean
numCheckV = IsNumeric(Vinput)
If numCheckV = False OrElse TextBox1.Text = "" Then
MsgBox("Please enter voltage!")
End If
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Apr 22, 2011
I am working on an app and I am a bit confused w/ threading. I understand the point of threading but I am not getting when to use a background worker thread vs. a standard thread vs. a thread pool. Can someone shed some light on when to use which? Right now, I am trying code an app that does stuff initially in a sequential order and then eventually must thread (otherwise it takes forever). The problem I am having w/ the sequential stuff (and threading later) is that I need a button to be able to stop execution of code. [Code]
I did the background worker on this first sequential operation because when I tried w/ out it, the text box didn't update at all until the web page contents were retrieved. Basically, the text box change of "Starting." doesn't show up until the web page is finished processing even though the assignment to the text box happens before that code.
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Feb 26, 2012
Is there any way to stop the execution of the code that's under a button if for example a certain condition is met?
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Mar 13, 2012
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
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Feb 10, 2011
I'm trying to safely kill a thread. In my button click I have:
try
dim bar as new foo()
dim mythread as New System.Threading.Thread(AddressOf bar.Start)
mythread.Start()
[code]....
When it goes to abort the thread I still get a thread abort error.
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Apr 29, 2011
I have this code:
Public Sub Submit(
ByVal reasonId As Integer,
ByVal email As String,
ByVal message As String
)
'[Argument validation code here]
EmailController.sendMail(reasonId, email, message)
End Sub
I want to spin this off in a new thread so Submit() returns right after creating and start the thread.In C#, I could do something like this:new Thread(() => { EmailController.sendMail(reasonId, email, message)}).Start();
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Oct 17, 2010
I have a webservice with a webmethod that accepts an XML from a client via POST (don't know if this really matters), validates XML and the data inside, and then processes the XML and returns an answer to the client.At moment, I have a problem with large XMLs; it takes too long for the XML preprocessing to finish, and the clients timeout expires.
Instead of increasing the timeout of the client I thought I could maybe separate the XML validation from the XML processing by starting a new thread after the validation which processes the XML and at the same time return the validation answer to the client. (the processing won't start if the XML is not valid.
Now my question is: Will opening the new thread increase memory usage? normally I would guess it will (for normal applications) but here I am returning an answer to the client and essentially ending the process of the main thread.
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.ComponentModel
[code]....
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Jun 11, 2009
I have an application which has a thread running which makes constant calls to a server. Occasionally, the calls become unresponsive, and I would like to stop and then restart the thread.How do I do this? I can't use mythread.Abort() because then it doesn't allow me to start the thread again.
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Nov 18, 2011
I'm in the Progress of changing a big Application from Singlethread logic to Multithread logic. I'm currently move Dataloading Logic into a sperate thread, and work with callbacks after they are finished. I have Synclocks in place in order to ensure threadsafty. But sonetimes the Synclocks wait even if there is no other thread with the same synclock active. Is there any way to find out what witch thread they are waiting for, and why? BTW, I have FW45 installed, may that be the reason, since it'S a inplace upgrade for FW40?
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Jan 24, 2012
I am making use of a serial port in a class. I am raising an event from that class to my form calling the class. Event contains data received... I wish to simply populate a textbox from the raised event.Now I am not specifically creating a seperate thread, but I get the normal crossthreading error when trying to update my textbox on the UI, so my assumption is that the serial port and its internal methods probably creates its own threads...Regardless, I am a bit confused as to how to properly implement an invoke, from my main form, pointing to the thread in the instantiated class...
Dim WithEvents tmpRS232 As New clsRS232
Private Sub but_txt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles but_txt.Click
tmpRS232.Set_com_port("COM8", 38400)
[code]....
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Apr 20, 2011
How do I ensure that a process has a thread on each processor?
What I am asking is how do I address processors to ensure a thread is running on it?
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