asp.net ÐÞ¸Äweb.conif <connectionStrings>

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private void Button1_Click(object sender, System.EventArgs e)
{
string filename=Server.MapPath("/") + @"\web.config";
XmlDocument  xmldoc= new XmlDocument();
xmldoc.Load(filename);

XmlNodeList topM=xmldoc.DocumentElement.ChildNodes;
foreach(XmlElement element in topM)
{
if(element.Name.ToLower()=="appsettings")
{
XmlNodeList _node=element.ChildNodes;
if ( _node.Count >0 )
{
foreach(XmlElement el in _node)
{
if(el.Attributes["key"].InnerXml.ToLower()==this.DropDownList1.SelectedItem.Value.ToLower())
{
el.Attributes["value"].Value=this.TextBox1.Text;
}
}
}
}
}
xmldoc.Save(filename);
}

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http://blog.csdn.net/zhoufoxcn/archive/2008/11/10/3265141.aspx

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public static void UpdateConfig(string conName, string conString,string configfilePath)       
{         
XmlDocument xmlDoc = new XmlDocument();         
xmlDoc.Load(configfilePath);