转自：http://blog.csdn.net/taoyinzhou/article/details/1906996
app.config 修改后，如果使用cofnigurationManager立即读取，不能获取修改后的值，只能获取缓存中的原值。使用下面直接操场xml文件的方式可以动态读写配置文件。
using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Xml;
namespace TaoNet.Common.TaoCommon
{
/// <summary>
/// C#中动态读写App.config配置文件
/// </summary>
public class AppConfig
{
public AppConfig()
{
///
/// TODO: 在此处添加构造函数逻辑
///
}
/// <summary>
/// 写操作
/// </summary>
/// <param name="strExecutablePath"></param>
/// <param name="AppKey"></param>
/// <param name="AppValue"></param>
public static void ConfigSetValue(string strExecutablePath,string AppKey, string AppValue)
{
XmlDocument xDoc = new XmlDocument();
//获取可执行文件的路径和名称
xDoc.Load(strExecutablePath + ".config");
XmlNode xNode;
XmlElement xElem1;
XmlElement xElem2;
xNode = xDoc.SelectSingleNode("//connectionStrings");
// xDoc.Load(System.Windows.Forms.Application.ExecutablePath + ".config");
xElem1 = (XmlElement)xNode.SelectSingleNode("//add[@name='" + AppKey + "']");
if (xElem1 != null) xElem1.SetAttribute("connectionString", AppValue);
else
{
xElem2 = xDoc.CreateElement("add");
xElem2.SetAttribute("name", AppKey);
xElem2.SetAttribute("connectionString", AppValue);
xNode.AppendChild(xElem2);
}
xDoc.Save(strExecutablePath + ".config");
}
/// <summary>
/// 读操作
/// </summary>
/// <param name="strExecutablePath"></param>
/// <param name="appKey"></param>
/// <returns></returns>
public string ConfigGetValue(string strExecutablePath, string appKey)
{
XmlDocument xDoc = new XmlDocument();
try
{
xDoc.Load(strExecutablePath + ".config");
XmlNode xNode;
XmlElement xElem;
xNode = xDoc.SelectSingleNode("//appSettings");
xElem = (XmlElement)xNode.SelectSingleNode("//add[@key='" + appKey + "']");
if (xElem != null)
return xElem.GetAttribute("value");
else
return "";
}
catch (Exception)
{
return "";
}
}
}
}