private string OutputPrice()
        {
            string sql = "select * from YuyaoPrice where ClassId=1 and SmallId=435";
            DataTable dt = DBclass.ExecSel(sql);
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                string a = dt.Rows[i]["NewPrice"].ToString();
                string b = ",";
                string c = a + b;
                Price = c.ToString();
                
            }
            return Price;
          
        }
 public string Price = string.Empty;

        protected void Page_Load(object sender, EventArgs e)
        {
            Price = OutputPrice();
            Response.Write(Price.ToString());//读出来只有：15900，
        }

 private List<string> OutputPrice()
        {
            string sql = "select * from YuyaoPrice where ClassId=1 and SmallId=435";
            DataTable dt = DBclass.ExecSel(sql);
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                string a = dt.Rows[i]["NewPrice"].ToString();
                string b = ",";
                string c = a + b;
                Prices.Add(c.ToString());
            }
            return Prices;

        }
        public List<string> Prices = new List<string>();

        protected void Page_Load(object sender, EventArgs e)
        {
            Prices = OutputPrice();

            foreach (string Price in Prices)
            {
                Response.Write(Price.ToString());//读出来只有：15900，
            }
        }

------解决方案--------------------
你这样是循环赋值，并没有追加，肯定最多只有一个了。

------解决方案--------------------
探讨

都不行。。。。


------解决方案--------------------
注意红色部分