web.config中自定义配置项读取

（一）配置  
  1.配置示例代码.  
      <?xml   version="1.0"   encoding="utf-8"   ?>  
  <configuration>  
  <appSettings>  
  <!--数据库配置-->  
  <add   key="DBHost"   value   ="192.168.0.2"   />  
  <add   key="DBName"   value="NorthWind"   />  
  <add   key="DBUser"   value="sa"   />  
  <add   key="DBPass"   value=""   />  
  <add   key="DBMaxConn"   value="50"   />  
  <add   key="DBMinConn"   value="3"   />  
  <add   key="DBConnTimeOut"   value="3"   />  
  </appSettings>      
  </configuration>  
   
       
  (二).用法  
  2.打开命名空间  
  using   System.Configuration;  
  3.读取示例  
  string   dbhost=ConfigurationSettings.AppSettings["DBHost"].Trim();  
  string   dbname=ConfigurationSettings.AppSettings["DBName"].Trim();  
  string   dbuser=ConfigurationSettings.AppSettings["DBUser"].Trim();  
  string   dbpass=ConfigurationSettings.AppSettings["DBPass"].Trim();