asp.net中gridview的查询、分页、编辑更新、删除的实例代码

                        CategoryId = sdr.GetInt32(4)
                    };

                    dals.Add(dal);
                }
            }
        }
        finally
        {
            //，关闭数据连接（释放资源）
            con.Close();
        }
        return dals;
    }

    public static void Add(ProductInfo dal)
    {
        string sql = "insert into Product(productName,unitprice,special,categoryId) values(@productName,@unitprice,@special,@categoryId)";

        SqlConnection con = new DBConnection().Con;
        SqlCommand cmd = con.CreateCommand();

        cmd.CommandText = sql;
        //配参数
        cmd.Parameters.Add(new SqlParameter("@productName",dal.ProductName));
        cmd.Parameters.Add(new SqlParameter("@unitprice",dal.Unitprice));
        cmd.Parameters.Add(new SqlParameter("@special", dal.Special));
        cmd.Parameters.Add(new SqlParameter("@categoryId", dal.CategoryId));

        con.Open();
        try
        {
            cmd.ExecuteNonQuery();
        }
        finally {
            con.Close();
        }

    }
    public static void Update(ProductInfo dal)
    {
        string sql = "update Product set productName=@productName,unitprice=@unitprice,special=@special,categoryId=@categoryId where productId=@productId";

        SqlConnection con = new DBConnection().Con;
        SqlCommand cmd = con.CreateCommand();