BackgroundWorker multithread access to form

Question

I am using 5 BackgroundWorker objects running at the same time for a certain purpose, and all of them have to change the same label. How do I do that? How do I modify the form from more than one thread then? And how do i do it in case i want to change a public string?

Accepted Answer

Use Control.Invoke with a delegate.

In your background worker thread, instead of saying

```
label4.Text = "Hello";
```

say

```
label4.Invoke(new Action(() =>
{
  label4.Text = "Hello";
}
));
```

Everything inside the { } executes on the control's thread, so you avoid the exception.

This allows you to do arbitrary changes to your user interface from a `BackgroundWorker` rather than just reporting progress.

BackgroundWorker multithread access to form

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