简单的连接数据库

/**/////App.config 文件内容

<?xml version="1.0" encoding="utf-8" ?>
<configuration >
  <connectionStrings >
    <add name ="OLEDB" connectionString="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:C#BoyangMISinDebugBoyangDB.mdb;Persist Security Info=True"/>
  </connectionStrings>
</configuration>

/**/////////////Connectionstr.cs 类
using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;
namespace BoyangMIS
...{
    class Connectionstr
    ...{
        public static string ConnectionString = ConfigurationManager.ConnectionStrings["OLEDB"].ConnectionString;
    }
}
/**///////////实现
string connstr = Connectionstr.ConnectionString;

   OleDbConnection oleconn = new OleDbConntion(connstr);