/*
  * Deletes a candidate
  */
 private void buttonDelete_Click(object sender, EventArgs e)
 {
     if (listBoxCandidate.SelectedIndex != -1)
     {
         Candidate candidate = (Candidate)listBoxCandidate.SelectedItem;
         controller.delete(candidate.Id.ToString());
     }
     else
     {
         System.Windows.Forms.MessageBox.Show("You must select a candidate.");
     }
 }