Multi-Thead Collection Was Modified / Enumeration Operation Might Not Execute
Nov 28, 2010
I have a multithreaded app that is throwing the following error.Collection was modified; enumeration operation might not execute.[code]I'm pretty sure the collection is being modified by another thread. I attempted to fix the problem with the SyncLock's but clearly I'm missing something here.I thought I could lock the object by properly using SyncLocks, am I just not locking the right object(s)? Or am I completely missing something here.Besides using SyncLocks what other options do I have to prevent this error. I was thinking perhaps a global variable to keep track critical code sections so that no 2 threads enter.I'm also a little confused about what collection is being modified my first guess was CLResultsDataTable. ResultsDataTable, but I'm not sure.This is an older project I just recently picked back up so I'm still stepping through a lot of code to try to figure out how/why this is happening
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Aug 4, 2011
We have some third party code that is causing some misery at the moment due to throwing the above error: it is slightly odd because it is an intermittent error. Here is the method that is causing the issue:
Private Shared Sub IntLocateDictionaries(ByVal haystack As ExpDictionary,
ByVal needlearray() As Object, _
ByVal resultarray() As Object, ByVal removemarks As Boolean)
Dim i As Integer
Dim item As Object
[Code] .....
I understand that this error is usually caused by trying to modify a collection whilst enumerating around it, hence why I've added logging on the only line that looks like might alter the collection... Since adding the logging we have still experienced the issue but NO LOGGING appears: this isn't surprising since if you look at the parameters on the calling line (the only place this Sub is called from) - removemarks is passed as False - this will be passed all the way down through the recursive calls and so that line which calls .Remove never gets executed....the fact we don't see logging proves this....
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Feb 17, 2012
I am working on a project where I have a personnel class. The records stored in the class are populated a few records per second. At the time I am inserting the records, I have to check the same class to ensure the same record is not added twice. Since I am looping through the class using "For Each", I get a message "Collection was modified; enumeration operation may not execute".
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Mar 11, 2009
i'm getting the following error: "COLLECTION WAS MODIFIED; ENUMERATION OPERATION MAY NOT EXECUTE."
The stack trace is ;
at System.Collections.SortedList.SortedListEnumerator.MoveNext()
at SatcomDiscoverySocket.clsGatewaySend.SendViaGatewaySend() in C:Documents and Settingsjim.SATCOM_DOMAINMy DocumentsVisual Studio 2005ProjectsSatcom Discovery Socket ServerSatcomDiscoverySocketSatcomDiscoverySocketThread PollingclsGatewaySend.vb:line 60
The line in question is but I don't believe that to be true I think its the line above it;GatewaySendEntry = Nothing The code is below. I can't figure out why, it's causing the error at that line and how to fix it.
[Code]...
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Sep 7, 2011
I have the following classes:
Product, Service and OrderItem
Product and Service must inherit OrderItem. So basically I want to store OrderItem object in my shopping cart and these object are store in a list.
Public MustInherit Class OrderItem
Private m_enuItemType As TypeOfItem = TypeOfItem.None
Private m_strUserID As Integer[code].....
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Oct 15, 2009
I have this flood-fill algorithm, based on a queue (I tried the recursive method but pictures are too big and it was causing stack overflow).The problem is that when it makes the second pass in the for-each loop, the program crashes and compiler gives me the message "Collection was modified; enumeration operation may not execute.".Well, of course I know the collection was modified (it supposed to be!) since I am adding necessary items to it on-the-fly within the loop. What I cannot understand is why it happens since the for-each is based on the remaining items in the collection and not in a numeric index.
Below, the actual code:
Code:
Public Sub FloodFill(ByVal myx As Integer, ByVal myy As Integer)
Dim icoord As coordinate
Dim ocoord As coordinate
[code]....
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Dec 29, 2011
This is what happened: on the form load of my application i created a background worker to bind collection (records from database filled in the dataset) on my control. but the problem is when the i updated the records on the database it throws an error if i run this procedure again.
If xControl.InvokeRequired Then
Dim MyDelegate As New InitializeDataBinding_Delegate(AddressOf InitializeDataBinding)
Invoke(MyDelegate, New Object() {xControl, xQuery, xPrimaryKey}) ' ERROR HERE SAYING: Collection was modified; enumeration operation may not execute.
[Code]...
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Oct 27, 2011
I'm getting a Collection was modified; enumeration operation may not execute error every time I try to close this form. I suspect it has something to do with the StringBuilder() which I have declared in the starting form (Details1). I have already spent hours looking for the problem. It does not throw an error when I debug, only when I install on other machines.
[Code]...
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Oct 15, 2011
I am encountering an error when looping through datarows. I searched SO and tried the solutions, but no luck. Collection was modified; enumeration operation might not execute.
Dim dRow As DataRow
For Each dRow In dt.Rows
dt.Rows.Add(dRow("CustNum"), dRow("SalesRepName"), dRow("mgrid"), "=""" & dRow("midValue") & """", dRow("dba"), dRow("sysDate"), dRow("statusID"))
Next
The error occurs the first time the code hits "Next". What would be causing Collection was modified; enumeration operation might not execute.How can I resolve this error?
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Jan 10, 2011
I'd like some help with this error that other users has when they launch the app I created. I will copy / paste the error
Tittle: Collection was modified; enumeration operation may not execute.
Error:
System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)
at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)
[code].....
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Sep 20, 2010
I'm getting this error when I deploy a VB.NET application and for the life of me I cannot figure out why.I do not get this error when I run the app from the IDE and the test machine I am deploying it to has a similar configuration to the dev machine...Windows 7 & .NET 3.51 SP1 and 4.0.The app bombs out when the main form is loaded after logging in. I've narrowed it down to the main form because if I load another form from login and then open the main form, this happens.
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Apr 15, 2010
I realize this has been covered a million times before but with threading sometimes a problem is app specific. I have a multithreaded app that assigns a url to a thread which it then fetches and crawls. Now the function where I collect each threads items I have added synclocks assuming this would avoid alterations. But I get the "collection was modified, enumeration operation may not execute" error. look at my code:
For Each landingPage As String In landingPages
'logger.constructLog("Working on landingPage link: " & landingPage & " at " & DateTime.Now.ToString, True)
[Code]....
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Dec 30, 2009
I have a form with a listview, and it operates as I expect it to, but when I close the form the debugger stops on the me.close() method and pulls up the collection was modified;enumeration operation may not execute error. this occurs even when I do nothing in the program and just try to run and close it.
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Sep 16, 2011
When I close some of the forms I have opened in my project, i get an error that says "Collection was modified, Enumeration operation may not execute"I used a Try/Catch error handler on one of the forms and it stopped the error from popping up, but I want to know what I can do so that this does not keep happening.
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Nov 1, 2011
I have a logout menu option in my MDI application. On log out I want to close all open forms. currently i am using following code snippet to achieve this;
For Each f As Form In My.Application.OpenForms
If f.Name = Me.Name Then
For Each child As Form In f.MdiChildren
[code]....
It is working perfect in my test environment, even though I expected For Each loop will throw "Collection was modified; enumeration operation may not execute" exception. since on each child form Close() calls, f.MdiChidren collection get modified, that surprised me a lot. Can anybody tell me why it's not throwing that exception?However it throws "Collection was modified; enumeration operation may not execute" in a client system.
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Apr 5, 2011
I've looked around at other forums and have seen that this is thrown because I am adding items to a collection in a for each statement. If I understand that right, I need a different way to populate my combobox here's the code.
[Code]...
This gets a list of all of the Shafts in the DB. I only need the name of the Shafts to be loaded into the combobox. What can I do to accomplish this without modifying the collection?
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Dec 23, 2011
I get that error any time my form closes(Me.Close), even if I don't do anything to the form at all exept load another form like this: Form2.Show Me.Close().
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May 18, 2012
I have some code that i cant work out why its happening and how to fix it. What im attempting to do is loop through the controls in a gridview and replace it with another control along with the text
Dim i As Integer
Dim row As GridViewRow
Dim rowCell As TableCellCollection = row.Cells
[Code].....
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Feb 16, 2011
I have a dataset returned after executing a sql query. below is my code to access the returned dataset and I seem to get this error sometimes and not all the time this code executes
Private Sub Timer1_Elapsed(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs) Handles Timer1.Elapsed
Dim currentMethod As String = MethodBase.GetCurrentMethod.Name
[Code].....
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Feb 10, 2010
I'm adding multi-threading facilities for the first time. I have a function that is wrapped to be run in a separated thread. This function retrieves data (text) from a combobox and it works for sure without multi-threading.
When I call it as multi-threaded, I get the following error when I try to retrieve the data from the cmobobox: Cross-thread operation not valid: Control 'cmb1stBL' accessed from a thread other than the thread it was created on.
It looks like a restriction of thread-safety... I assume that the child thread cannot read from his parent, to make sure that he doesn't change his parent data. So how can I read the data from the combobox? Should I read the comoboxbox data before calling the child thread?
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Dec 21, 2011
I'm have a data management program. I've fixed everything in it, except when I run my Insert or update commands on a different computer I've installed it on, JIT tells me that the collection has be modified, it then gives me the option to continue or quit. I know it's been modified, the user knows it's been modified, how do I get rid of that?
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Apr 27, 2010
I am trying to refresh my combobox when an item is selected and added the highlighted code as shown below; [code]Items collection cannot be modified when the DataSource property is set.
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Jun 17, 2010
I have a combobobox on my form, and I use the following code to populate the data from SQL Server:
cbname.DataSource = DSAssetName.Tables(0)
cbname.DisplayMember = "IDWLNAME"
cbname.ValueMember = "FIDWID"
[code].....
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Feb 13, 2010
I have two tables "Person" and "Alias" in a one to many relationship. I have a DGV for "Person" and want to use a combobox for the Aliases. I also have a textbox and a button for the user to type the alias name and click the button to add the alias name to the combobox and update the dataset. I keep getting the "Items collection cannot be modified when the DataSource property is set." Error. But if i use a DGV instead of a combobox for aliases, I have no errors and everything works fine. If I remove the datasource property for the combobox it will not get populated with the data already entered, so how, or can I, set it up where the combobox gets populated when the form loads and able to add items to the combobox????
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Aug 26, 2011
Like i want it to read the lines i have in the text file but i get an error Each time i press the button Why?
Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
Dim objreader As New System.IO.StreamReader("C:UsersJamesDesktopMusicas.txt")
Do Until objreader.EndOfStream
[code]....
Error:
Quote:
Items collection cannot be modified when the DataSource property is set.
Error line
Quote:
ListBox1.Items.Add(objreader)
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Jul 27, 2007
I have looked at multiple posts regarding this issue, but can't seem to find a solution. To keep it simple I have an Access database with a single table. It does have a field as a primary key. When I click the save icon on the Binding Navigator I get this error having to do with the following code:
Me.Validate()
Me.TitlesBindingSource.EndEdit()
Me.TitlesTableAdapter.Update(Me.VFCurvesDataSet.Titles)
I cannot set the Refresh the Data Table check box in Advanced Options of the TableAdapter Configuration Wizard as it is grayed out. Once again, I have a primary key.
The posts I have reviewed indicate that an UpdateCommand needs to be created, but I can't understand how it should be done. W
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Nov 11, 2005
I get an error when I try to edit a cell that already containts data. What am I missing? be as explicit as I am very new at this.
[Code]...
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May 18, 2007
I want to make an application in VB.NET and I want this application to work as follows, There will be an array of items on which I want to perform a specific operation (MyTask), with the help of multiple threads.For example, say, the array is holding 12 items in it, and I want to create 3 threads to do the work,
Thread 1: Reads the first item from the array and goes to perform the specific operation (MyTask).
Thread 2: Reads the second item from the array and goes to perform the operation MyTask
Thread 3: Reads the third itm from the array and goes to perform the Mytask.
Now once Thread 1 completes the operatin MyTask, I want to assign 4th item from the array to the Thread 1 to continue the process.Once Thread 2 completes the operatin MyTask, I want to assign 5th item from the array to the Thread 2 to continue the process and so on... until all the items from the array is processed. Also, the function taking 5 arguments out of which 4 arguments will be same. Only one argument will vary and it will take the keywords one by one as input parameter.
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Apr 3, 2012
ok here is my code :
[Code]...
What's happening is, i see the threads stop after the function dwnld is completed. So i first check for the state (12 means background and unstarted). On case 12 start the thread and in case 16 (stopped) remove that particular thread and add a different thread like i add 10 above. Also there is a check when the i counter reaches last number, restart the whole loop by assigning i=0.
The program downloads some web pages, the url is passed from the listbox2. The geturl will pass the url and remove it from the list. So when the listbox is empty, exit the for loop. But the above code is running for only 11 times and it does not restart. I tried using a lable and goto but it simple hangs. What i want is to maintain 10 threads to keep downloading the web pages and when the list is empty, exit the function.
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May 28, 2010
I have just received an interesting feedback from a VB.NET customer using our product - for some reason intellisense hidden a certain enumeration value.After a small testing I have found that this is likely a bug in IntelliSense: [URL]..To be honest, I did not expect this problem with such a basic stuff like this. Have you seen this in the past? For me, it doesn't work in all VS versions...
Anyway, feel free to track this issue if you are coding in VB.NET.
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