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.
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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?
View 1 RepliesI'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
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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.
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
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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.
what is the best way to identify memory leaks from a vb.net 3.5 windows application.
View 1 RepliesMy application has 1 main form and three other forms which raise events to my main form. I noticed that the memory starts at 77,000 K and increases substationally over a few hours maby be to 250,000k and ever increases.The main form has a dataset and a bound datagridview which gets refreshed with data. Basically it's a taxi booking application. The booking form raises an event to the main form and the main form refreshes the jobs and displays them on the dgv.
View 8 RepliesIf I always need to call RemoveHandler after using AddHandler, where is the best place to do so? I have searched several similar questions as follows, but I do not quite understand.When and where to call the RemoveHandler in VB.NET? AddHandler/RemoveHandler Not Disposing Correctly..I thought garbage collection in c# or vb.net will take care of unused objects. Also, in vb.net designer, it automatically generates Dispose Sub. So I did not pay attention to programally releasing resource at all. Will I have any memory leak problems? Please kindly provide me some links/documents for me to start learning.[code]
View 1 Repliesfrom the vb web:
Quote:
Caution:
Because this is a static event, you must detach your event handlers when your application is disposed, or memory leaks will result.my interpretation is that "detach your event handlers" only means those that i've added using AddHandler? the ones using Handles keyword will be safe right?
I want to check for leaks?This code is run at load of the MDI form.So Gdi and User get set then.This code also runs when a child closes.The counts at closing do not equal those at load.If there is no leaks, should they?If not, why not?Can I do something to make this work?Maybe force GC?
Static Gdi As Integer = 0
Static User As Integer = 0
If Gdi = 0 Then
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I am working to a VB.NET windows forms projet in .NET 1.1. And I have this type of architecture, very simplified.[code]...
Depending of the type of test I am doing I create an instance of a specific test derived from BaseTestLogic. But I found that after hundreds of object creations I can have StackOverflow exception.
I checked my code and saw that I forgot to remove the handler to Timer Tick. The question is, where and when is it correct to remove hadler?
Do I need to implement the IDisposable interface in the base class and RemoveHandler in Dispose?
the concept of AddHandler/RemoveHandler with a very simple example?
View 28 RepliesHow do I use RemoveHandler with anonymous methods? This is how I add a handler for MyEvent event of the class MyClass
AddHandler MyClass.MyEvent, Sub()
...
End Sub
How do I then use RemoveHandler to remove the handler for the MyEvent event
The VB documentation shows the Syntax for RemoveHandler statement as:
RemoveHandler event, AddressOf eventhandler and shows a Sample usage as:
To streamline code, I increasingly rely on lambda expressions. But I may have hit against the wall in the attempt of removing an event handler set by a lambda expression. This really eludes me. The code below shows two samples: Alt1 uses a plain lambda expression as delegate and works fine: the object size increases as the numeric control varies. However, the drawback is that the handler cannot be removed:
RemoveHandler Me.upDnScale.ValueChanged, Sub(sender As Object, e As Object) ScaleObject1(sender, e, objTgt)
According to this MSDN article, a variable should be used to set/remove lambda based handlers. Alt2 shows a couple of attempts, but none works.
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Using VB2008 Express I'm getting the following warning on a RemoveHandler statement and subsequent issues since the event is still hooked. Warning 1 The 'AddressOf' expression has no effect in this context because the method argument to 'AddressOf' requires a relaxed conversion to the delegate type of the event. Assign the 'AddressOf' expression to a variable, and use the variable to add or remove the method as the handler.
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I'm getting a bit more fluent in VB.Net, but am still a bit green around the edges in certain aspects. I'm creating custom controls, and am starting to rely heavily on AddHandlers to manage them.Until recently, I didn't realize that you can add multiple event handlers for the same control and same address
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The above code would create 10,000 copies of the same event, and if I would click on combobutton1, the event would fire 10,000 times. I only need to fire the event once, but sometimes my code is a bit circular, and there may be an instance where two or more addhandlers are designated for a given control and address. Is there a way to have a loop on my custom dispose event where it would look something like:
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Or better yet, remove all events from a control(On a side note, is there any way in the debug mode to see all the active events attached to a control?)
I have a class set up to hold values on a registration form (VB.NET, MVC), and among the properties is a Password property:
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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.
View 10 RepliesIm 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?
I am using the following code
This error occurs :
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.
Public Class FormRegEnumValue
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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
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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!
Does vb 2010 have a 'REQUIRED" property or control that allow you to make a textbox a "required" field? I googled and saw something about required property in controls in toolbox but somehow I could not find it anywhere in my vb 2010 toolbox. Would it be easier to write it? Does anyone have sample code?
View 6 RepliesI have been trying to implement the jQuery weekcalendar using .net. What I can't seem to figure out is why weekcalendar states events.events is undefined after I make an ajax call to a webmethod I created which returns JSON. Below is the relevant code:
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I want to make Keybord events and mouse events for learning and educational Purpose.
1. In Form any object like A "picture box" move by Arrow keys .
2. Picture Box Contain many Picture i want change Picture With next and Previos By Arrow keys.
3. I contain Voice of alphabet in Mp3.When i Press any button in textbox then its work.
4. Mouse Pointer Change My Own.
5. I click any Object or any thing By mouse its noice clicking sound like Tik Tik Tik.... Question No 3 is very hard to do . but not im possible
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.
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