Description: In Windows Forms if you launch a new thread and want to update controls on your form, you must use Invoke. This example updates the Text property of a Label.

Link: http://www.codekeep.net/snippets/3b1cd8c5-cf11-4eb2-b52f-78dccc2d6de9.aspx

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First create a method to make the UI updates, and define a delegate that
matches the signature of the method.
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private delegate void setStatusDelegate(string status);

private void setStatus(string status)
{
	lblStatus.Text = status;
}

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From another thread, you can use the Invoke method of the form to
execute the setStatus method.
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Invoke(new setStatusDelegate(setStatus), "This is the status text");