读取配置config文件

<system.net>
    <mailSettings>
        <smtp from="Fish.Q.Li@newegg.com">
            <network />
        </smtp>
    </mailSettings>
</system.net>

读取上面↑的xml代码{

mtpSection section = ConfigurationManager.GetSection("system.net/mailSettings/smtp") as SmtpSection;
labMailFrom.Text = "Mail From: " + section.From;

}

写入配置文件：

Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);

SmtpSection section = config.GetSection("system.net/mailSettings/smtp") as SmtpSection;
section.From = "Fish.Q.Li@newegg.com2";

config.Save();

如果配置文件为以下格式的：

<MySection444>
    <add key="aa" value="11111"></add>
    <add key="bb" value="22222"></add>
    <add key="cc" value="33333"></add>
</MySection444>

读取方法：

public class MySection4 : ConfigurationSection    // 所有配置节点都要选择这个基类
{
    private static readonly ConfigurationProperty s_property
        = new ConfigurationProperty(string.Empty, typeof(MyKeyValueCollection), null, 
                                        ConfigurationPropertyOptions.IsDefaultCollection);
    
    [ConfigurationProperty("", Options = ConfigurationPropertyOptions.IsDefaultCollection)]
    public MyKeyValueCollection KeyValues
    {
        get
        {
            return (MyKeyValueCollection)base[s_property];
        }
    }
}


[ConfigurationCollection(typeof(MyKeyValueSetting))]
public class MyKeyValueCollection : ConfigurationElementCollection        // 自定义一个集合
{
    // 基本上，所有的方法都只要简单地调用基类的实现就可以了。

    public MyKeyValueCollection() : base(StringComparer.OrdinalIgnoreCase)    // 忽略大小写
    {
    }

    // 其实关键就是这个索引器。但它也是调用基类的实现，只是做下类型转就行了。
    new public MyKeyValueSetting this[string name]
    {
        get
        {
            return (MyKeyValueSetting)base.BaseGet(name);
        }
    }

    // 下面二个方法中抽象类中必须要实现的。
    protected override ConfigurationElement CreateNewElement()
    {
        return new MyKeyValueSetting();
    }
    protected override object GetElementKey(ConfigurationElement element)
    {
        return ((MyKeyValueSetting)element).Key;
    }

    // 说明：如果不需要在代码中修改集合，可以不实现Add, Clear, Remove
    public void Add(MyKeyValueSetting setting)
    {
        this.BaseAdd(setting);
    }
    public void Clear()
    {
        base.BaseClear();
    }
    public void Remove(string name)
    {
        base.BaseRemove(name);
    }
}

public class MyKeyValueSetting : ConfigurationElement    // 集合中的每个元素
{
    [ConfigurationProperty("key", IsRequired = true)]
    public string Key
    {
        get { return this["key"].ToString(); }
        set { this["key"] = value; }
    }

    [ConfigurationProperty("value", IsRequired = true)]
    public string Value
    {
        get { return this["value"].ToString(); }
        set { this["value"] = value; }
    }
}

下面是demo方法

public class EsbHeaders : ConfigurationElement
    {
        [ConfigurationProperty("children", IsDefaultCollection = true)]
        [ConfigurationCollection(typeof(EsbHeader), AddItemName = "header")]
        public EsbHeaderCollection Headers
        {
            get { return (EsbHeaderCollection)base["children"]; }
            set { base["children"] = value; }
        }
    }

    public class EsbHeaderCollection : ConfigurationElementCollection
    {
        protected override ConfigurationElement CreateNewElement()
        {
            return new EsbHeader();
        }

        protected override object GetElementKey(ConfigurationElement element)
        {
            return ((EsbHeader)element).Identity;
        }


        public new EsbHeader this[string key]
        {
            get { return (EsbHeader)base.BaseGet(key); }
        }

        public EsbHeader this[int index]
        {
            get { return (EsbHeader)base.BaseGet(index); }
        }

        public List<EsbHeader> ToList()
        {
            var list = new List<EsbHeader>();
            IEnumerator ie = this.GetEnumerator();
            while (ie.MoveNext())
                list.Add(ie.Current as EsbHeader);
            return list;
        }
    }

    public class EsbHeader : ConfigurationElement, IRequestEntity
    {
        private string identity = string.Empty;
        [ConfigurationProperty("identity", IsRequired = false)]
        public string Identity
        {
            get
            {
                if (identity == string.Empty)
                    return this.SERVICE_CODE;
                else
                    return identity;
            }
            set { identity = value; }
        }


        [ConfigurationProperty("service", IsRequired = true)]
        public string SERVICE_CODE
        {
            get { return (string)base["service"]; }
            set { base["service"] = value; }
        }

        [ConfigurationProperty("version", IsRequired = true)]
        public string VERSION
        {
            get { return (string)base["version"]; }
            set { base["version"] = value; }
        }

        [ConfigurationProperty("consumer", IsRequired = true)]
        public string CONSUMER_CODE
        {
            get { return (string)base["consumer"]; }
            set { base["consumer"] = value; }
        }

        [ConfigurationProperty("password", IsRequired = true)]
        public string PASSWORD
        {
            get { return (string)base["password"]; }
            set { base["password"] = value; }
        }

        [ConfigurationProperty("desc", IsRequired = true)]
        public string Description
        {
            get { return (string)base["desc"]; }
            set { base["desc"] = value; }
        }


        [ConfigurationProperty("ext1", IsRequired = false)]
        public string EXT1
        {
            get { return (string)base["ext1"]; }
            set { base["ext1"] = value; }
        }
        [ConfigurationProperty("ext2", IsRequired = false)]
        public string EXT2
        {
            get { return (string)base["ext2"]; }
            set { base["ext2"] = value; }
        }
        [ConfigurationProperty("ext3", IsRequired = false)]
        public string EXT3
        {
            get { return (string)base["ext3"]; }
            set { base["ext3"] = value; }
        }

demo-config

<sinosoft>
    <esb>
      <headers>
        <children>
          <header service="s-1" version="1" consumer="CS-1/65/" password="12436798" desc=""></header>
          <header service="s-2" version="1" consumer="CS-1/6" password="4235465687" desc=""></header>
          <header service="s-3" version="1" consumer="CS-1/-01" password="24346" desc=""></header>

        </children>
      </headers>
    </esb>
    <reports>
      <sms url="" userid="TCBB" password="456"></sms>
    </reports>
  </sinosoft>

小结：
1. 为每个集合中的参数项创建一个从ConfigurationElement继承的派生类。
2. 为集合创建一个从ConfigurationElementCollection继承的集合类，具体在实现时主要就是调用基类的方法。
3. 在创建ConfigurationSection的继承类时，创建一个表示集合的属性就可以了，注意[ConfigurationProperty]的各参数。

参考自：http://www.cnblogs.com/fish-li/archive/2011/12/18/2292037.html#_labelStart