I was just wondering if mixing SyncLock blocks and Monitor.Enter/Exit statements is dangerous. I know SyncLock uses Monitor and a Try block in the background, but are there any problems with using the two together for thread synchronization?
View 1 RepliesI want to make a process monitor tool with WMI that monitor the processes created or deleted, but the code will not work. Note to reference System.Management,
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Can I monitor the registry for changes similar to how sysinternals process monitor does it in VB? I have checked many different articles and C# samples but not come any closer to getting an answer, I would like to know if there an easier way (a VB sample perhaps)that you folks can share. Ultimately I'd like to be able monitor other things too like file system, processes etc but wonder most about how the registry can be done in VB...Would using system.management be a start? Or WMI? if so is there a nice VB sample..
View 3 RepliesI have the following windows service file:
Imports System.ServiceProcess
Imports System.IO
Public Class fswService
[Code].....
2 problems: first, intellisense error saying: 'fswService' is a type and cannot be used as an expression. second, I can not figure out a way to pass on to the service the path of the folder to watch (which is stored at My.Settings.userPath).
I am pretty new to multi-threading in general and I would like to know how can I lock a shared integer variable to not be accessed by other threads while it is read/updated by an other thread.When I try do do SyncLock myInteger, I get that error : Error 6 'SyncLock' operand cannot be of type 'Integer' because 'Integer' is not a reference type.
Here a simplified example of what I mean
Private Shared myInteger As Integer
Private Sub MySub()
SyncLock myInteger ' This does not work
' read/write a new value to myInteger
End SyncLock
End Sub
MySub is called by multiple instances of the class, and running in multiple threads?
Is there simple way to SyncLock an object that can be null? And before you ask for it, yes, I know that it isn't logical to perform a SyncLock on a null variable. However, that would simplify my code because right now, I have no choice but to perform a null check all over the place before calling a SyncLock.
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If I have two Synclocks
synclock a
synclock b
end synclock
[code].....
I was wondering if this is known / expected behavior. By design?Is it documented somewhere?
My 'real' code does need something to keep one thread from accessing a listview while another is busy clearing and refreshing the Items collection, so it's not as easy as omitting the synclock section in the example below (The SyncLock in my case is on the ListView).
This code, which can be pasted over a new empty form's user code class, deadlocks during the Invoke call. It doesn't reach the entry point of SetText (setting a brakpoint there, the deadlock occurs before the breakpoint is hit).[cod]e...
I have an application that requires several threads, otherwise the main UI thread would end up frozen.i am after a little advice as i have not really don alot of threaded applications.
First Question;
I have a thread which handles data coming in from the serial port( this wil become much more complicated), is it safe to use a synclock on the serialport object : -
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Suppose I have a byte array, Private Data as Byte(). This array is private within a class. The class provides public functions for reading and writing to Data. This class can be accessed by multiple threads, so I want to avoid a situation where reading from it and writing from it don't happen at the same time.
For now, I am using SyncLock to avoid issues. Can I put SyncLock Data in just the write functions, or does it need to be in the read functions? Or, both? I don't have a specific code example in mind. I am just curious if there is any benefit to locking for both read and write functions if the writing functions' SyncLock will make writing have exclusive access to it in the first place.
I'm trying to SyncLock my DataTable, to avoid problems with multithreading and stuff. But it doesn't seems to work. I'm trying to lock a DataTable wich is acceseed inside a nested for-loop:
vb.net
SyncLock radiolopere
For Each row As DataRowView In tableview
[code].....
I have a class that contains a List(of T) used in a multithreaded application. I have three methods Get, Add and Remove where these access and modify the List(of T). I was using SyncLock to lock m_List any time I queried it for the desired object as well as when I added or removed objects. However I'm curious as to if there is a performance gain by simply locking m_List when I add an object or remove an object as opposed to when I'm searching for a desired object?
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I have a List of objects shared by multiple threads, it sometimes generate IndexOutOfRangeException when trying to Clear. While searching for solution I found that I should use SyncLock while accessing the List. But my question if what is the importance of lockObject in SyncLock block
E.g. while clearing myList
Can I use
Synclock myList
myList.Clear
End SyncLock
or lockObject should be different from myList?
What I think about sysnclock is "lock is obtained for object specified as lockObject". What if I specify list to be cleared as lockObject, shouldn't the compiler supposed to obtain the exclusive access to list before clearing it ?
Once again Invoke has come back to haunt me! I have an application that has some background threads, serial communications and obviously a GUI. Now, the serial ports received incoming messages as events and these get processed and incoming data is logged both to a file and also appended to a RTB in the GUI (done using Invoke if InvokeRequired is true).Now, under normal circumstances everything is super happy and runs quite nicely but when stressed I reach some sort of deadlock.
What happens is I have two methods AddOutput and RemoveOutput. These both sync over an object SyncOutput As Object. When messages are received on the serial port they are processed and depending on whether or not a response is required AddOutput is called. This adds out going messages to a dictionary which is then accessed by a thread and the messages are sent out. If an acknowledgement message is received then the corresponding message in the dictionary is removed.
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If completedOrders.Count <> 0 Then
For i = 0 To completedOrders.Count - 1
SyncLock completedOrders
'Do some work, for example this:
Dim text As String = completedOrders(0).getCN & " " & completedOrders(0).getDeviceName & " "
End SyncLock
Next
End If
Is a synclock needed before the if statement or for loop? In other words. When you call methods like .length or .count is it necessary to synclock them or can another thread be writing to it at the same time. CompletedOrders is a generic list of a class.
Ok so I coded this app that generates a number/word and it will upload to my database. Speed wasn't the issue when my db was under 1million entry. Now that I got about 100million entry it takes a few mins to upload.I worked with threading before but now I want all my threads to access this function that will give them a string. Now here is the problem, if 2 or more thread access the function at the same time, it will crash.How can I by pass that?I read about SyncLock. Can I use SyncLock on my function on each thread?
View 1 RepliesSay I have some code that does this:
Public Function AppendToLogFile(ByVal s As String) As Boolean
Dim success As Boolean = True
Dim fs As IO.FileStream = Nothing
[Code].....
First of all: is it a problem that I have that Try/Catch/Finally block inside of a SyncLock?
Second of all: suppose this code runs, on an event, potentially many times within a small timeframe--say, ten times in one second. Is it OK to have it SyncLock like this, or would it make more sense to have it add a line to a Queue, and then write all the lines from the Queue to the file on a timer that goes off, say, every second?
Is it possible to skip a code block when a synclock is active?
For instance:
A object of class Bicycle is used by thread 1 and has a synclock on it.
Then thread 2 comes along and needs to know if the lights of the bike are working. But if there is a synclock active then thread 2 just forgets about checking the lights and goes to make a delicious chocolate pie.
Can someone who is using a 64 bit machine help me pintpoint this crash to either the VS2010 IDE itself or one of the plugins I have installed?
It's the code fragment below. When I copy & paste it into the Main() function of a new VB.Net console app on my Win7 64 bit machine, the VS IDE crashes and dies onthe spot, every time I try it.
Doing exactly the same on a 32 bit XP machine, nothing abnormal happens.
The 64 bit machine does have some IDE plug-ins installed, the biggest of which is DevExpress (the free version), so i think either one of those or the fact that the IDE is running on 64 bit must be the culprit.
This is the code. The static variable can also be made a module-level variable, with the same result.
I'm having trouble working out how to lock my application out of a section of code while it waits for a response from an external program've used Synclock on a section of code with the Me object in the expression. In this Synclock I call an overridden ShowDialog method of a dialog box, which has a timeout parameter, but does return the value from the underlying ShowDialog function call ,once the timer is setup. Works like this.
SyncLock Me
Dim frmDlgWithTimeout As New frmDlgWithTimeout ' dialog box with overridden ShowDialog '
Dim res As DialogResult = frmDlgWithTimeout.ShowDialog(10 * 1000) ' 10 sec timeout '
[code]....
i have some test code which i run at every load of a page in my asp.net website [Code] the "dotrace" simply add a record to a log table in the db. now the right result would be that i should have the entries in the db in order "entered","exiting","exited" but actually when i look in the db i see first 2 "entered" then 2 "exiting" etc. meaning that the multi-threading is working ok, but not the synclock. is that correct?
and how can this be fixed? the real code will be adding records to the db and might be called from several pages of different sessions, but the same code must not run twice concurrently. if i open multiple pages at once, they still clash some times. but if i'm correct, the issue is now not with the synclock as much as with the httpruntime.cache, because when using a standard property, on one page, the code works 100%. so how can i make sure that 2 threads, even from totally different sessions never run the trylock simultaneously?
I am trying to get a handle on SyncLock and multithreading, but I am having some trouble wrapping my head around exactly how it should be implemented. I have a Public Class Utilities with a many Shared Functions. I want to make sure that each function can only be executed when there are no other concurrent calls to the same function. So If I have 2 functions, A and B in a Public Class Utilities, what is the syntax so that a function "locks" while it is being executed, preventing any subsequent calls until the "locking" thread has completed?
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Public Class Utilities
Public Shared Function A (ByRef i As Integer) As Integer
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I know I need to wrap the statements of execution in a SyncLock block, but I am unsure of the scope of the parameter used with SyncLock...is it private to the function, class, etc? Can the same object be used to lock both functions if they are independent?
I am using Synclock to prevent multiple threads from logging text messages to the same file at the same time, but this doesn't seem to work:I get frequent sharing errors on the logfile, within the synclock block.The Synclock is using the variable holding the filename, because it exists all the time and because it is always the same object, whatever class instance or thread I'm in.[code]Despite using Synclock and a Using block around the code, I keep getting this error in the sw.WriteLine(Msg) line:System.IO.IOException: The process cannot access the file '(filename)' because it is being used by another process.Should I use some other type of object than a string to synchronize on?I cannot use a user interface object (button or so) because it is a windows service project.It was written and compiled in Visual Studio 2008, but targeting the 2.0 framework because it has to be able to run on some old Win2000 machines.
View 12 RepliesI'm on my way to MSDN but thought I'd stop by here first because the answers are usually more cogent.I have a test bed that mimmicks my product app. The general architecture is a factory that builds/instantiates a number of objects (device controllers) that are scalable in number based on requirement. Each object has a threaded portion that reads a device. This way, each object can read its own device simultaneously with all the others. To perform the read, the object calls a routine in a Module that houses the device interfaces. Interestingly (and happily), it seems like each thread has its own copy of the Module routine.
The test bed seems to verify what I'm seeing in the app. In the testbed, a 500 mil second delay is substituted for the device call. Even enclosing the test module portion that hosts the delay in a Synclock results in multi-threaded execution of the pseudo device call. I haven't tested for data yet, but this seems to indicate that when the module routine is called from controller object, it too carries it's own copy of the data just like the calling object. As a long time c++ programmer...that don't quite seem right.
I want to be able to have the Level of my Mic in my Form. I want a Progressbar that tracks how high my voice is just like in Windows Movie Maker or In Msn Messinger when you are doing a voice Chat there is a Progressbar like object that shows how loud it is...
View 17 RepliesI've a (challenge?) question for you, it's possible to monitor an swf embedded in a Form, so we can know when it stopped?[code]...
View 12 RepliesSo, when a user is running my application, how do I monitor for a particular key press? I am looking at this for my reference[url]...
View 7 RepliesI am creating a tool for monitor turn off function,I should be able to get wether monitor is switched on or switch off from my code.I got solutions only to switch on or switch off the monitor, any one can help me how can we dedect if a monitor is turned on or off?
View 1 Replies[code]Seems to fetch data from my one and only internal IDE drive.The line objWriter.Write("Active: {0} ", queryObj("Active")) does not work if you change up the data in between the first set of quotes. Thus changing Active: {0} to Active: {1} causes an error that the Try Catch doesn't catch (this for...next is in a try catch).I assumed that the stuff inside the quotes was just text and could be changed to anything? Why doesn't the try catch catch it?Doesn't read a USB external drive when attached.i changed {0} to {1} and it crashes.
View 1 RepliesI have put together an app to monitor several directories. The basic principle is to replicate from a Master directory to a Shared directory when specific criteria is met (specific file types are changed, renamed or deleted within the Master directory)Everything seems to work fine with excpetion to MS Office documents. e.g. If I work on a .bmp and save it, it will trigger a changed event. However, with office documents (Word in this example), it appears to rename the MYDOC.DOC file to <freefile>.TMP then rename a different <freefile>.TMP to MYDOC.DOC. This would not be a problem if it was to trigger the Changed or Created event for MYDOC.DOC, but it doesn't. It wouldn't be so bad if the first TMP file was named the same as the second TMP file as I could mirror the process using the Renamed event.I can not filter out TMP files as we use TMP files within the Master directory, albeit for a different purpose.I would use an off the shelf produt, but the files need to be copied to different shared directories based on specific criteria so I can not seem to find a suitable product that fits my needs.
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