Using combos within a BackgroundWorker

Question

Possible Duplicate:
Cross-thread operation not valid: Control accessed from a thread other than the thread it was created on

I having problems trying to get things to work with a BackgroundWorker.

I have a checkbox which when click I want to call the BackgroundWorkers RunWorkerAsync method:

    private void checkBoxLoadRecords_CheckedChanged(object sender, EventArgs e)
    {
        bw.RunWorkerAsync();
    }

So within the DoWork event I call the SelectionChangeComitted event on one of my combos:

    void bw_DoWork(object sender, DoWorkEventArgs e)
    {
        comboSelectedIDs_SelectionChangeCommitted(sender, e);
    }

Within the SelectionChangeComitted method I receive an error on the first line where I try to retrieve the ID into a variable. The error I receive is: Cross-thread operation not valid: Control 'comboSelectedIDs' accessed from a thread other than the thread it was created on.

void comboSelectedIDs_SelectionChangeCommitted(object sender, EventArgs e)
{
    int idToUse = (int)multiSelectedIDs.SelectedValue; //Errors here!
    SetupNamesCombo(idToUse);
}

How do I get round this problem?

I think I'm going to have a similar problem when using my custom controls as they use the combos text value and I would like to get that in the BackgroundWorker.

I'm using C# 4.0

Thanks in advance.

Note: don't call event handler - create method and call it. – Renatas M. Aug 13 '12 at 13:28 — Renatas M., Aug 13 '12 at 13:28

score 0 · Answer 1 · answered Aug 13 '12 at 13:15

0

Use the Dispatcher class to access to the UI elements from different threads:

        Deployment.Current.Dispatcher.BeginInvoke(() =>
        {
            int idToUse = (int)multiSelectedIDs.SelectedValue;
        });

Or if you are in a code behind file you can just do this without the Deployment.Current.

answered Aug 13 '12 at 13:15

laszlokiss88

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What namespace do I need to import to use this? Thanks – Sun Aug 13 '12 at 13:23
Sorry, Deployment.Current.Dispathcer is in Silverlight. If you use WPF, then App.Current.Dispatcher... – laszlokiss88 Aug 13 '12 at 13:26

score 0 · Answer 2 · answered Aug 13 '12 at 13:15

0

You cannot access UI controls in any thread other than the UI thread.

One solution is to save the values of the UI controls in a separate POCO object, so you can access them from the background worker.

answered Aug 13 '12 at 13:15

Maarten

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Using combos within a BackgroundWorker

2 Answers2