Necessary To Detach Event Handlers To Ensure That Memory Is Cleaned Up And That There Are Not Memory Leaks?
Jan 20, 2010
I have a BackgroundWorker object that I instantiated to perform a DB process on a background thread ansynchronously. I have event handlers for DoWork and RunWorkerCompleted. I can tell that the BackgroundWorker is disposing of itself because I added a message box into the Disposed event handler.Is it necessary to detach the event handlers to ensure that the memory is cleaned up and that there are not memory leaks?
I've noticed that every time I start a new thread in my program, the memory usage jumps about 1000k and it never goes back down. I have ensured that the thread is no longer running, and only one instance of my worker thread is ever running at a time. I am using ThreadPool.QueueUserWorkItem and ASyncOperation to get stuff done. The program starts using a Sub Main in a module that uses STAThread; I read that using STAThread instead of MTAThread makes it impossible for the Garbage Collector to get in and consider objects for garbage collection. However, when I change the STAThread to an MTAThread, the WebBrowser control in my frmMain cannot be instantiated.
I get this exception:
Code: An unhandled exception of type 'System.Threading.ThreadStateException' occurred in System.Windows.Forms.dll
Additional information: ActiveX control '8856f961-340a-11d0-a96b-00c04fd705a2' cannot be instantiated because the current thread is not in a single-threaded apartment. I do threading with the WebBrowser control, so will using MTAThread fix my problem? If so, how should I partition my code so that the WebBrowser control won't be affected by the above exception? I call the thread repeatedly with a timer (although only one instance ever runs at a time), and my program's memory usage starts at about 5000k and can jump to 300,000k+ depending on many times the thread needs to be called.
I've been using a simple mouse hook and some accessiblity api stuff to retreive caption under mouse (ObjectFromPoint) and accessibility api for events (ObjectFromEvent).It seems like there is memory leaks with unmanaged callbacks.With the global mouse hook it seems there is 4 - 8k of ram added every time the mouse is just moved even though I only monitor mousedown and mouseup with:
Private Const WM_LBUTTONDOWN As UInteger = &H201 Private Const WM_LBUTTONUP As UInteger = &H202 Private Const WM_MBUTTONDOWN As UInteger = &H207
[code]....
And with accessibility it seems there is also memory issues with my code. Is this to do with delegates?I only managed to find one mention on the mouse hook issues which led me in to a dead end.A long shot and maybe not even needed but I was wondering, if these mem leaks can't be stopped, would it free up the memory if I used threads which could be exited and new ones started eg.mem usage 3000k of which 1000k is leaked mem (for round figures) I exit global mouse hook thread and start a new m-hook thread.would this free up the memory? If so, how would i do this, not use threading before.
I have attempted to understand the behind-the-scenes stuff for Events several times. I must have read at least a dozen articles but there is still some ambiguity in my head.
What is the best way to write functions in Microsoft.NET (VB) to avoid memory leaks. I have always followed this style:
Public Sub TestMemoryLeak() Dim testCon As SqlConnection Try
[code].....
Here the connection reference is created before the TRY clause and is initialised after the TRY clause. I believe the connection is always closed and dereferenced even if an exception is thrown. Is this good practice? I see a lot of code that creates references and dereferences in the TRY clause, but this would mean that the memory is not correctly handled if an exception is thrown. Some developers say they don't like to clean up in the finally clause.
In VB 2005, I am calling a C++ DLL function that returns the address in memory and size in bytes of a jpeg image. How can I load that jpeg image directly from memory into a picture box in my VB form? I cannot afford to save it to disk first.
Im getting a problem with one of my programs I have made in visual basic.NET where it gives me a memory error when i debug the program in the IDE. the exact error is this: "Attempted to read or write protected memory. This is often an indication that other memory is corrupt". My program basically has a few forms with text fields on that get their text values from an access database on the same hard drive. Im wondering if im doing something wrong because my program just seems to eat up memory whenever it does anything. For example I have one form that has a combobox on it and when you change the drop down list selection it retreives a few strings from the database and puts them into the relevant text boxes, if you keep changing the selection then the memory usage (in task manager) just keeps going up and up. occasionally I get the error mentioned above when debugging but in my built version of the program it throws an exception everytime the memory usage gets past 49K.
Also I noticed when debugging in the "immediate window" frame I get the following message often:A first chance exception of type 'System. Invalid OperationException' occurred in System.Data.dll...Do I need to somehow be "releasing" the memory that is used to gather data once it becomes redundant?
Attempted to read or write protected memory. This is often an indication that other memory is corrupt. Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
QuoteSystem.AccessViolationException was unhandled Message="Attempted to read or write protected memory. This is often an indication that other memory is corrupt." Source="System.Windows.Forms"
Im designing a web browser and i continue to receive this error after going to about 3 websites it crashes with that error.
I cannot use Visual Basic 2008 at all. When I go to "new project" and choose "Windows Form Application" I get this error.I have tried multiple uninstall/reinstall with no result.A microsoft reply to this suggested that I needed: " .NET Framework 2.0 Service Pack 1 " I checked, and I did not have the .netframework 2.0 service Pack 1. When I tried to download and install the above from Microsoft.com, the istaller said that "it was not allowsed" and I was not able to install the service pack 1.
I tried Uninstalling net framework 3.5, 3.0, 2.0 and then reinstalling .netframework 2.0 sevice pack 1; then reinstalling Visual basic 2008 express edition. At the reinstall of Visual basic 2008, .netframework 2.0 sevice pack 1 is unistalled by .net framework service pack 2.When I check the foruims for simiar problems, the formus are mostly for Visual basic 5.0, or other programs that I do not have.
Here is the programs I have installed:
Operating system: Windows XP Microsoft .net framework 1.1 Microsoft .NET framwork 1.1 Hotfix(KB928366) Microsoft .Net Framework 2.0 Service Pack 2
[code]....
All the security updates and hotfixes for Widows XP.
The follow code can be called about 6K times on the server it is run on then gets a out of memory error in the last catch statement. I don't see what is wrong with the code, it works well up until the out of memory..
Public Function AddUserToGroup(ByVal sSamAccountName As String, ByVal sGroupName As String) As Boolean Try Dim returnStatus As Boolean = True[code]......
I have two forms, Form1 and Form2. Form2 has a button to show OpenFileDialog. I call Form2 from Form1 by a button. My startUp Form is Form1. When i start debugging, i press my Form1's button to show my Form2, it shows, but when i click On Form2's Button to show OpenFileDialog it is giving me exception that
"Attempted to read or write protected memory. This is often an indication that other memory is corrupt."
When i set my startup Form to Form2 and click Form2's Button to show OpenFileDialog then it shows!
I have a new problem with this same Form Printing project and I get exactly the same exception but from the different point of code:
line 538: d.PrintFunction(c, typePrint, mp, x, y, extendedHeight, ScanForChildControls)
The exception type is System.AccessViolationException and it says (after I translate it from my own language in which the message is given in my pc, into English):"Protected memory was tried to be read or written. This often indicates that the other memory is damaged"
I am getting the following error: "Attempted to read or write protected memory. This is often an indication that other memory is corrupt". i am using interop service.
This code was put together for a one time run. It's purpose is to count all the pages in a group of images. After about 6000 of 1,250,000 images in ##X it throws an "out of memory" error. Besides it being thrown together for a one time run does anybody see anything obvious that could be causing the error?
it is clear that an Object handling an event has to unregister himself of that event before it ends, to avoid not been cleared from the memory by the CG - especially when it lives longer than the "Event Raiser" object. But, on the other hand, I wonder if it is possible to encounter this problem on the web server... Is it possible that the server will keep this object alive, even if the execution context (i.e. the web session) has died? Are'nt all the objects related to a session cleared with the session itself?
I have been searching for memory leaks in my application and come down to this weirdness. I have a class which implements IDisposable and one single event in it as shown below:[code]
I am just curious, if there is some way to attach handler to my derived classes base event, if I know EventInfo and I have Delegate to handler function. I have tried MyEvent.AddHandler(CType(Me, BaseClassType), MyDelegate) already, but no positive result at all. Consider being in need of attaching handler to custom event at runtime, while derived class possibly shadows this event.
When I utilize AddHandler in VB to add my own method to the Click event :
AddHandler Button.Click, AddressOf myButton_Click
I see that my code executes last - after other event handlers for the Button_Click event. Is there a way to insert my event handler in front of other events so that it executes first?
Public Class Form1 Public Event Evt1(ByVal c As c1) Public Event Evt2(ByVal c As c2)
[code]...
However, it seems to be invalid syntax, as the signature of OnEvt1OrEvt2 doesn't match that of Evt2.
Edit: The above code seems to work fine for everyone but me, but it doesn't compile for me in VS2005 SP1.The error message is something like:Error BC31029: The method 'Private Sub OnEvt1OrEvt2(c As WindowsApplication1.c1)' can not handle the event 'Public Event Evt2(c As WindowsApplication1.c2)' because the signatures do not match.
is it allowed to use more than one Sub to handle the same event ? For example , may I have 2 separate subs to handle the Load event of a form ? Will they fight each other ?I have tested it and it seems to work fine , nevertheless I thought I'd ask you . In case you wonder , there is no great deal , I just want to copy the same lines of code in more forms so I am doing it just in favor of the looking aspect .
I have a panel control on a win form, to which I dynamically add a custom control.The custom control inherits UserControls and in the New() sub, I assign the control a GUID.When a control is added to the form, a variable of type List(Of T) holds the details of where i put the control and the size of it.
Within the custom control class there is a delete method. When the method, which deletes the custom control, is run I want the details of that custom control removed.I think I need to use event handlers but I do not know how to handle these when the controls are added dynamically.
I have a problem, in Winform or mobile developing, When I newed some buttons in my code(never drew on the form), how can I add the click events to them and use it?
How do I create an event with many handlers. I use the followingo code but it failed. Am I missing something?
Protected Sub myhandler_CheckedChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles CrdCb1.CheckedChanged, CrdCb2.CheckedChanged End Sub
I was editing my code and after deleting a button from a toolstrip vs locked up and trashed the designer.vb code. Now I have all my form code but many of the control objects (e.g. buttons, listviews ..etc) have been deleted. I've re-added the control but none of the events associated with the control (e.g. _click) work. If I delete the event handler code and add a new one the paste in the code it works fine
