protected void OnAddWatch()
        {
            List <string> exps = new List <string> ();

            foreach (TreePath tp in Selection.GetSelectedRows())
            {
                TreeIter it;
                if (store.GetIter(out it, tp))
                {
                    string exp = GetFullExpression(it);
                    exps.Add(exp);
                }
            }
            foreach (string s in exps)
            {
                DebuggingService.AddWatch(s);
            }
        }