/// <summary>
 /// Invokes the SelectedItem event; called whenever item in the listBox is selected
 /// </summary>
 /// <param name="e"></param>
 private void OnSelectedStatement(SelectedStatementEventArgs e)
 {
     if (SelectedStatement != null)
         SelectedStatement(this, e);
 }
 /// <summary>
 /// when value in assist popup has been selected insert new statement with combobox.
 /// </summary>
 /// <param name="sender"></param>
 /// <param name="args"></param>
 private void OnSelectedStatement(object sender, SelectedStatementEventArgs args)
 {
     if (args != null)
     {
         Focus();
         //first remove last typed word
         RemoveLastWord();
         InsertStatementWithComboBox(args.SelectedStatement);
     }
 }