<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<connectionStrings> --方式1
<add name="strCon" connectionString="server=127.0.0.1;user id=sa; password=csw; database=testDB;"/>
</connectionStrings>

<appSettings> --方式2
<add key="ConnectionString" value="server=127.0.0.1;user id=sa; password=csw; database=testDB;"/>
<add key="ConStringEncrypt" value="true"/>
</appSettings>
</configuration>

1、首先先在工程里添加system.configuration.dll程序集的引用

2、写代码读取配置参数

方法一： string connStr= System.Configuration.ConfigurationManager.ConnectionStrings["strCon"].ToString();

方法二： string connStr= ConfigurationManager.AppSettings["ConnectionString"];