写法：
<configuration> <appSettings> <add key="connectionstring" value="server=127.0.0.1;uid=sa;pwd=123456;database=Power"/> </appSettings> </configuration>
调用：
string rode= System.Configuration.ConfigurationSettings.AppSettings["connectionstring"];
写法：
<connectionStrings> <add name="CONNECTIONS" connectionString="Server=10.10.10.1;Database=MyDBTest;Uid=sa;Pwd=sa" /> </connectionStrings>
调用：
string connectionstr = System.Configuration.ConfigurationSettings.AppSettings["CONNECTIONS"];
sql数据库连接字符串在APP.config配置文件内的两种写法
原文：http://www.cnblogs.com/yunquan/p/7383386.html