Про GuiAsync

public static void GuiAsync(this Dispatcher dispatcher, Action action, DispatcherPriority priority)
		{
			if (dispatcher == null)
				throw new ArgumentNullException("dispatcher");

			if (action == null)
				throw new ArgumentNullException("action");

			if (dispatcher.CheckAccess())
				action();
			else
				dispatcher.BeginInvoke(action, priority);
		}

        public void GuiAsync(MethodInvoker action)
        {
            if (action == null)
                throw new ArgumentNullException("action");

            if (!this.InvokeRequired)
                action();
            else
                this.Invoke(action);
        }