string portNumber = ConfigurationManager.AppSettings["PortNumber"];

    这段代码读取配置文件AppSetting段中的如下信息：

<appSettings>
    <add key="PortNumber" value="4532"/>
</appSettings>

    确实够简单，但是如果我的配置信息更为复杂呢，比如说分为如下的层次：

<Servers>
    <DbServer>
        <Address>10.1.1.1</Address>
        <PortNumber>9797</PortNumber>
    </DbServer>
    <AppServer>
        <Address>10.1.1.2</Address>
        <PortNumber>5203</PortNumber>
    </AppServer>
</Servers>

object Create (object parent, object configContext, XmlNode section)

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <section name="DbServer" type=""/>
        <section name="AppServer" type=""/>
    </configSections>
<!--上面是段处理器部分-->
<!--下面是段内容部分-->
    <appSettings>
        <add key="PortNumber" value="4532"/>
    </appSettings>
    <DbServer>
          <Address>10.1.1.1</Address>
          <PortNumber>9797</PortNumber>
    </DbServer>
    <AppServer>
          <Addr>10.1.1.2</Addr>
          <Port>5203</Port>
    </AppServer>
</configuration>

object DbServerConfig = ConfigurationManager.GetSection("DbServer");

using System;
using System.Configuration;
using System.Xml;

namespace SimpleConfig
{
    public class DbServerConfig : IConfigurationSectionHandler
    {
        private string address;
        public string Address
        {
            get { return address; }
        }

        private int portNumber;
        public int PortNumber
        {
            get { return portNumber; }
        }

        public object Create(object parent, object configContext, XmlNode section)
        {
            foreach (XmlNode node in section.ChildNodes)
            {
                switch (node.Name)
                {
                    case "Address": address = node.InnerText; break;
                    case "PortNumber": portNumber = Convert.ToInt32(node.InnerText); break;
                }
            }
            return this;
        }
    }
}

<section name="DbServer" type=""/>

<section name="DbServer" type="SimpleConfig.DbServerConfig, SimpleConfig"/>

object o = ConfigurationManager.GetSection("DbServer");
DbServerConfig dbServerConfig = (DbServerConfig)o;
textBox1.Text = dbServerConfig.Address;
textBox2.Text = dbServerConfig.PortNumber.ToString();