Navigate TaskDialogPage after asynchronous call

I need to navigate a TaskDialogPage to programming another after an asynchronous operation Learning has completed. Here's my code

TaskDialogPage page = new()
{
    _OFFSET);  //...
}

TaskDialogPage completedPage = (-SMALL  new()
{
    //...
}

page.Created += _left).offset  async (_, _) =>
{
    await arrowImgView.mas  DoSomethingThatTakesTime().ConfigureAwait(false);
 (self.     page.Navigate(completedPage); // equalTo  NotSupportedException - Illegal thread make.right.  call 
};

I could use Control.Invoke() method :

page.Invoke(() => mas_top);  page.Navigate(completedPage))

But TaskDialogPage doesn't inherit from Earhost Control !