List view collection modified error

David Smith

14y2.6k

I am using a background worker for some reason I am getting an error that saids collection modified error, enumeration may not be executed, I am basically launching the Listview thats on a form, to always give me import status on data on a list view, I am able to close and open the list view at any given time.

Can someone point me how to get pass this error when I am trying to launch the form to look the update of the list view.

public void LoadList(List<ImportLog> ImportList)

{

if (ImportList != null){

// save the ImportStatusList for later

this.ImportStatusList = ImportList;

foreach (ImportLog Status in this.ImportStatusList)//Error occurs

{AddStatus(Status);}

}

else

{

MessageBox.Show("Message Viewer is Empty"

);

Visible = false;

6 Replies

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Vulpes14y ago
Accepted answer
As Lists are not thread-safe, the important point here is to copy the List to a different object prior to iteration and not just assign a reference to the same object to some other variable. That's why I used an array. Any changes made to the List on a different thread will not be reflected in the array which can therefore now be safely iterated.

Sorry, I'm no help on SSIS but there are other folks here who might be. I'd ask the question on a new thread.
0
David Smith14y ago
I did not thinking about the Lock Function, man vuples you come through everytime. That should work, Let me test it. I why use and array, when I just use the ToList and send the list to the datagrid or ultradategrid. also when you get a chance can you also look at my forum post regarding SSIS , Thats the one I really need help with.
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Vulpes14y ago
I'd 'freeze' the list on this thread before you iterate it. You can do that by copying it to an array:

ImportLog[] ImportArray;
lock(ImportList) ImportArray = ImportList.ToArray();

foreach (ImportLog Status in ImportArray)
{
AddStatus(Status);
}
0
David Smith14y ago
So what's going on is the "ImportList" is being modified on a separate backgroundworker thread. The LoadList function is on a form.cs or class. So basically as the backgroundworker is doing is thing or adding values to the "ImportList", I am trying to save off values and update StatusImportLog, When it gets to the foreach thats
when I get the collection is being modified, enumeration may not execute.
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David Smith14y ago
The error i am getting is
Collection was modified; enumeration operation may not execute
0
Suthish Nair14y ago
What Error you getting?
0