You will required to have the Refresh applied on your textbox so it will display all the texts while the loop is running.
You will require to have a static class for ExtensionMethods that will contain your refresh routine.
public static class ExtensionMethods
{
private static Action EmptyDelegate = delegate() { };
public static void Refresh(this UIElement uiElement)
{
uiElement.Dispatcher.Invoke(DispatcherPriority.Render, EmptyDelegate);
}
}
now simply calling
txtTransferredData.Refresh()
will refresh your textbox text within loop as well.
I think this will work in your case.