[大数据]C#中 实现增删改查

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.SqlClient;


namespace ASP.NETDemo
{
    /// <summary>
    /// 通用数据访问类
    /// </summary>
    class SQLHelper
    {
        private static string connString = "Server=.;DataBase=StudentManageDB;Uid=sa;Pwd=sasa";

        /// <summary>
        /// 返回单一结果的查询,一行一列
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static object GetSingleResult(string sql)
        {
            SqlConnection conn = new SqlConnection(connString);
            SqlCommand cmd = new SqlCommand(sql, conn);
            conn.Open();
            object result = cmd.ExecuteScalar(); //执行查询
            conn.Close();
            return result;
        }
        /// <summary>
        /// 更新操作（insert update delete）
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static int Update(string sql)
        {
            SqlConnection conn = new SqlConnection(connString);
            SqlCommand cmd = new SqlCommand(sql, conn);
            conn.Open();
            int result = cmd.ExecuteNonQuery();
            conn.Close();
            return result;
        }
        /// <summary>
        /// 返回一个结果集
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static SqlDataReader GetReader(string sql)
        {
            SqlConnection conn = new SqlConnection(connString);
            SqlCommand cmd = new SqlCommand(sql, conn);
            conn.Open();
            return cmd.ExecuteReader(CommandBehavior.CloseConnection);
        }
    }
}

        static void Main(string[] args)
        {
            string sql = "select Count(*) from Students";
            object result = SQLHelper.GetSingleResult(sql);
            Console.WriteLine(result);
            Console.ReadLine();
        }

        static void Main(string[] args)
        {
            string sql = "update Students set StudentName='刘晶晶' where StudentId=100005";
            int result = SQLHelper.Update(sql);
            Console.WriteLine(result);
            Console.ReadLine();
        }

        static void Main(string[] args)
        {
            string sql = "select StudentName from Students";
            SqlDataReader objReader = SQLHelper.GetReader(sql);
            while (objReader.Read())
            {
                Console.WriteLine(objReader["StudentName"]);
            }
            objReader.Close();//关掉读取器（同时自动关闭关联的连接）
            Console.ReadLine();
        }