BackgroundWorker problem when accessing a List in DoWork

[schnandr]

Hi,

I have a user control which contains ListView. I copy all
ListViewItems into a separate List<ListViewIt emcalled
unfilteredItems .
I am using a BackgroundWorke r to filter the ListView. When I access
this list in the DoWork Handler I am getting an
InvalidOperatio nException that
the List was not created by this thread. Is there a way to solve this
problem?


Here some Code

public partial class ListCtrl : UserControl
{
private IListCtrlFilter filter;

private BackgroundWorke r filterWorker;

private List<ListViewIt emunfilterdItem s = new
List<ListViewIt em>();

...

void filterWorker_Do Work(object sender, DoWorkEventArgs e)
{

BackgroundWorke r worker = sender as BackgroundWorke r;

List<ListViewIt emunfiltered = e.Argument as
List<ListViewIt em>;

if filter;!= null)
{
listView.Items. Clear();
foreach (ListViewItem item in unfiltered)
{
if (worker.Cancell ationPending)
return;

if (filter.Include (item))
worker.ReportPr ogress(0, item);
}
}
}

void filterWorker_Pr ogressChanged(o bject sender,
ProgressChanged EventArgs e)
{
listView.Items. Add(e.UserState as ListViewItem);
}

...
}

Thanks for every hint

[Peter Duniho]

Re: BackgroundWorke r problem when accessing a List in DoWork

On Sat, 15 Nov 2008 23:06:09 -0800, schnandr
<andreas.schnei der@skillworks. dewrote:

Hi,
>
I have a user control which contains ListView. I copy all
ListViewItems into a separate List<ListViewIt emcalled
unfilteredItems .
I am using a BackgroundWorke r to filter the ListView. When I access
this list in the DoWork Handler I am getting an
InvalidOperatio nException that
the List was not created by this thread. Is there a way to solve this
problem?

Surely your error is complaining that the _ListView_ was not created by
the same thread. There should be no problem accessing an instance of
List<Tfrom a different thread than the one used to create it.

As for addressing the problem, the most obvious solution given that you're
using a BackgroundWorke r is to use exclusively the BackgroundWorke r events
to access the ListView itself. For example, don't clear the list until
the first time the ProgressChanged handler is called. Alternatively, you
can use Control.Invoke( ) if you really feel the need (but then it begs the
question as to why you're bothering with BackgroundWorke r :) ).

Search this newsgroup for terms like "cross-thread exception",
"control.invoke ", and "backgroundwork er" for more details.

Pete