How to display intellisence popup for custom key combinations?

 
        //Holds the List box control in Intellisence popup
        listbox = (sender as EditControl).Template.FindName("PART_IntellisenseBox", (sender as EditControl)) as ListBox;
 
        //Holds the Intellisence popup
        popup = (sender as EditControl).Template.FindName("PART_IntellisensePopup", (sender as EditControl)) as Popup;
 
        /// <summary>
        /// KeyDown1 event to check the key pressed
        /// </summary>
        private void EditSQL_KeyDown1(object sender, KeyEventArgs e)
        {
            items = new ObservableCollection<CustomIntellisenseItem>();
 
            if (e.Key == Key.E)
            {
                items = customItems;
                popup.Height = 200;
                //Set listbox visible
                listbox.Visibility = Visibility.Visible;
            }
            else
            {
                popup.Height = 0;
                //Set listbox as collapsed
                listbox.Visibility = Visibility.Collapsed;
            }
 
            editSQL.IntellisenseCustomItemsSource = items;
        }
 

 
 'Holds the List box control in Intellisence popup
 listbox = TryCast((TryCast(sender, EditControl)).Template.FindName("PART_IntellisenseBox", (TryCast(sender, EditControl))), ListBox)
 
 'Holds the Intellisence popup
 popup = TryCast((TryCast(sender, EditControl)).Template.FindName("PART_IntellisensePopup", (TryCast(sender, EditControl))), Popup)
 
 ''' <summary>
 ''' KeyDown1 event to check the key pressed
 ''' </summary>
 Private Sub EditSQL_KeyDown1(ByVal sender As Object, ByVal e As KeyEventArgs)
  items = New ObservableCollection(Of CustomIntellisenseItem)()
  If e.Key = Key.E Then
   items = customItems
   popup.Height = 200
   'Set listbox visible
   listbox.Visibility = Visibility.Visible
  Else
   popup.Height = 0
   'Set listbox as collapsed
   listbox.Visibility = Visibility.Collapsed
  End If
 
  editSQL.IntellisenseCustomItemsSource = items
 End Sub