private void Form1_Load(object sender, EventArgs e)//初始化sqlDependency，开始监听
        {
            dep.OnChange += new OnChangeEventHandler(dep_OnChange);
            SqlDependency.Start(conn.ConnectionString);
            ListStudent();
        }

       private void dep_OnChange(object sender, SqlNotificationEventArgs e)
//监听方法，每一次启动时总是提示e.Info为Invalid.(无法通知)
e也就是SqlNotificationInfo
        {
            DialogResult dR;
            dR = MessageBox.Show("The data has changed. Refresh?",e.Info.ToString(),MessageBoxButtons.YesNo,MessageBoxIcon.Question);
            if (dR == DialogResult.Yes)
            {
                this.Invoke(new PopulateList(ListStudent));
            }
        }

        private void ListStudent()//读取数据
        {
            productListBox.Items.Clear();
            conn.Open();
            SqlDataReader reader = cmd.ExecuteReader();
            while (reader.Read())
            {
                productListBox.Items.Add(reader["name"].ToString() + ":" + reader["sex"].ToString());
            }
            conn.Close();
        }


是否是要在sqlserver中启用相应的sql语句，才支持sqlDependenCy类?