support.cs

 public override void Action()
        {
            Application.ActiveDocument.CurrentSelection.Changed += CurrentSelection_Changed;
        }

        public void CurrentSelection_Changed(object sender, EventArgs e)
        {
            var selection = Application.ActiveDocument.CurrentSelection;
            MessageBox.Show(selection.SelectedItems.First.ClassDisplayName.ToString());
            Application.ActiveDocument.CurrentSelection.Changed -= CurrentSelection_Changed;

        }