private void Form1_Load(object sender, EventArgs e)
        {
            string comstring = "select Towaste from Con";
            SqlDataAdapter com = new SqlDataAdapter(comstring,DBHelp.connection);
            DataSet ds=new DataSet();
            com.Fill(ds, "Con");
            this.dataGridView1.DataSource = ds.Tables["Con"];

        }
这一句怎么用循环读出 Towaste 的值！