Ribbon _ribbon; // your main ribbon
RibbonDropDown _dropDown; // the dropdown context menu

public void ShowDropDown(Point screenCoordinates)
{
  // the function to invoke from your control context menu request callback
  List<RibbonItem> items;
  RibbonButton dummyButton;

  DisposeDropDown();  
  items = new List<RibbonItem>();
  dummyButton = new RibbonButton("");
  PopulateDropDown(items); // any function that takes care of creating/collecting the items from the ribbon
 // this ctor is only present in my temporary code
  _dropDown = new RibbonDropDown(dummyButton, items, _ribbon);
  _dropDown.Show(screenCoordinates);
}

public void PopulateDropDown(List<RibbonItem> items)
{
   RibbonButton btn;
   btn  = new RibbonButton("Test 1");
   btn .Click += RibbonButton_Click;
   items.Add(btn);
}

public void DisposeDropDown()
{
    if (_dropDown != null)
    {
        // if dropdown items were just created dynamically to be hosted in the context menu, we must dispose them

        foreach (RibbonItem oldItem in _dropDown.Items)
            oldItem.Click -= RibbonButton_Click;
        _dropDown.Dispose();
    }
}