<?xml version="1.0" encoding="utf-8" ?><configuration> <configSections>  <section name="SQLConfiguration" type="ConfigurationDemo.SQLConfiguration,ConfigurationDemo"/>  <section name="AccountConfiguration" type="ConfigurationDemo.AccountConfiguration,ConfigurationDemo"/> </configSections> <SQLConfiguration type="MSSQL" connectionString="server=.;integrated security=sspi;database=Northwind"></SQLConfiguration> <AccountConfiguration>  <users username="liunian" password="123456"></users> </AccountConfiguration> <system.net>  <mailSettings>   <smtp from="liunian@qq.com">    <network />   </smtp>  </mailSettings> </system.net></configuration>

  class SQLConfiguration : ConfigurationSection  {    [ConfigurationProperty("type", IsRequired = true)]    public string Type    {      get { return this["type"].ToString(); }      set { this["type"] = value; }    }    [ConfigurationProperty("connectionString", IsRequired = true)]    public string ConnectionString    {      get { return this["connectionString"].ToString(); }      set { this["connectionString"] = value; }    }  }

      SQLConfiguration sqlConfig = (SQLConfiguration)ConfigurationManager.GetSection("SQLConfiguration");      Console.WriteLine(sqlConfig.Type);      Console.WriteLine(sqlConfig.ConnectionString);

  public class AccountConfiguration : ConfigurationSection  {    [ConfigurationProperty("users", IsRequired = true)]    public AccountSectionElement Users    {      get { return (AccountSectionElement)this["users"]; }    }  }  public class AccountSectionElement : ConfigurationElement  {    [ConfigurationProperty("username", IsRequired = true)]    public string UserName    {      get { return this["username"].ToString(); }      set { this["username"] = value; }    }    [ConfigurationProperty("password", IsRequired = true)]    public string Password    {      get { return this["password"].ToString(); }      set { this["password"] = value; }    }  }

     AccountConfiguration accountConfig = (AccountConfiguration)ConfigurationManager.GetSection("AccountConfiguration");      Console.WriteLine(accountConfig.Users.UserName);      Console.WriteLine(accountConfig.Users.Password);

      Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);      SmtpSection section = config.GetSection("system.net/mailSettings/smtp") as SmtpSection;      Console.WriteLine(section.From);