DBHelper类可以用来连接数据库，对相应的数据库进行数据的增删改查操作。
方法一：直接编写DBHelper类（发布后无法在修改连接信息）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;
using System.Data.SqlClient;
namespace DAL
{
    public class DBHelper
    {
        private static SqlConnection con;
        private static SqlCommand cmd;
        private static SqlDataAdapter da;
        private static SqlDataReader reder;
        public static void Init()
        {

            if (con == null)
            {
            con = new SqlConnection("server=172.28.80.210  ;database=mp;uid=hga;pwd=hga.makepower.cc");
            }
            if (con.State == ConnectionState.Closed)//处于关闭状态
            {
                con.Open();
            }
            if (con.State == ConnectionState.Broken)//处于中断状态
            {
                con.Close();
                con.Open();
            }

        }
        //查询
        public static DataTable GetTable(string sql)
        {
            Init();
            DataTable dt = new DataTable();
            da = new SqlDataAdapter(sql, con);


            try
            {
                da.Fill(dt);
                return dt;
            }
            catch (Exception)
            {

                return null;
            }
        }
        //增删改
        public static bool ExcuteSql(string sql)
        {
            Init();
            cmd = new SqlCommand(sql, con);
            try
            {
                cmd.ExecuteNonQuery();
                return true;
            }
            catch (Exception)
            {

                return false;
            }
        }
        public static SqlDataReader GetReader(string sql)
        {
            Init();
            SqlCommand cmd = new SqlCommand(sql, con);
            SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
            return dr;

        }
        //显示文本
        public static string ExcuetText(string sql)
        {
            try
            {
                Init();
                SqlCommand cmd = new SqlCommand(sql, con);
                string result = cmd.ExecuteScalar().ToString();
                return result;
            }
            catch (Exception)
            {

                throw;
            }
            finally
            {

                con.Close();
            }
        }
        //调用存储过程
      public static DataTable GetList(string sqlDBO, params SqlParameter[] values)
        {
            Init();
            DataTable ds = new DataTable();
            SqlCommand cmd = new SqlCommand(sqlDBO, con);
            cmd.CommandType = CommandType.StoredProcedure; //指定命令类型为存储过程
            cmd.Parameters.AddRange(values);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(ds);
            return ds;
        }

    }
}

方法二.先在Web.config 文件中加入要连接的数据库（当你发布了网站时可以在confing文件中修改连接的数据库信息）

    <add key="ConnectionString" value="server=./数据库服务器名称;database=Demo;uid=sa;pwd=123456"/>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;
using System.Data.SqlClient;
namespace DAL
{
    public class DBHelper
    {
        private static SqlConnection con;
        private static SqlCommand cmd;
        private static SqlDataAdapter da;
        private static SqlDataReader reder;
        public static void Init()
        {

            if (con == null)
            {
            con=new SqlConnection(System.Configuration.ConfigurationManager.AppSettings["ConnectionString"].ToString());
            }
            if (con.State == ConnectionState.Closed)//处于关闭状态
            {
                con.Open();
            }
            if (con.State == ConnectionState.Broken)//处于中断状态
            {
                con.Close();
                con.Open();
            }

        }
        //查询
        public static DataTable GetTable(string sql)
        {
            Init();
            DataTable dt = new DataTable();
            da = new SqlDataAdapter(sql, con);


            try
            {
                da.Fill(dt);
                return dt;
            }
            catch (Exception)
            {

                return null;
            }
        }
        //增删改
        public static bool ExcuteSql(string sql)
        {
            Init();
            cmd = new SqlCommand(sql, con);
            try
            {
                cmd.ExecuteNonQuery();
                return true;
            }
            catch (Exception)
            {

                return false;
            }
        }
        public static SqlDataReader GetReader(string sql)
        {
            Init();
            SqlCommand cmd = new SqlCommand(sql, con);
            SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
            return dr;

        }
        public static string ExcuetText(string sql)
        {
            try
            {
                Init();
                SqlCommand cmd = new SqlCommand(sql, con);
                string result = cmd.ExecuteScalar().ToString();
                return result;
            }
            catch (Exception)
            {

                throw;
            }
            finally
            {

                con.Close();
            }
        }
        //调用存储过程
         public static DataTable GetList(string sqlDBO, params SqlParameter[] values)
        {
            Init();
            DataTable ds = new DataTable();
            SqlCommand cmd = new SqlCommand(sqlDBO, con);
            cmd.CommandType = CommandType.StoredProcedure; //指定命令类型为存储过程
            cmd.Parameters.AddRange(values);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(ds);
            return ds;
          
          


        }

    }
}

扩展

存储过程的调用方法

  SqlParameter[] para = new SqlParameter[]
          {
    new SqlParameter("@sname","张三"),
    new SqlParameter("@id","1")
          };           
     DBHelper.GetList("z_cxsj", para);