DAL层中添加根据CONFIG内容执行SQL语句类

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

namespace DAL
{
    public class ClassTree
    {
        //数据库配置修改并编译才能生效呢
        private string connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["classTreeConnectionString"].ConnectionString;
       // private string connectionString="Data Source=.;Initial Catalog=classTree;User ID=sa;pwd=123456;";
        /// <summary>
        /// 根据sql返回DataSet
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public DataSet getDataSetBySql(string sql)
        {
            SqlConnection conn = new SqlConnection(connectionString);
            SqlDataAdapter da = new SqlDataAdapter(sql, conn);
            DataSet ds = new DataSet();
            da.Fill(ds);
            return ds;
        }
        /// <summary>
        /// 根据传入的sql语句
        /// </summary>
        /// <param name="sql"></param>
        public void ExecSQl(string sql)
        {
            SqlConnection conn = new SqlConnection(connectionString);
            conn.Open();
            SqlCommand command = new SqlCommand(sql, conn);
            command.ExecuteNonQuery();
            conn.Close();
        }
    }
}

 附： </configSections>节点下添加

 <dataConfiguration defaultDatabase="classTreeConnectionString" />
 <connectionStrings>
 
  <add name="classTreeConnectionString" connectionString="Data Source=IP;Initial Catalog=classTree;User ID=sa;Password=PWD" providerName="System.Data.SqlClient" />
 </connectionStrings>