Runtime Web.config / App.config Editing

摘自http://www.eggheadcafe.com/articles/20030907.asp

using System;
using System.Xml;  
using System.Configuration;
using System.Collections;
using System.Reflection;  
using System.Diagnostics ;

public enum   ConfigFileType
{
 WebConfig ,
 AppConfig
}

public class AppConfig : System.Configuration.AppSettingsReader
{ 
 public string  docName = String.Empty;
 private  XmlNode node=null;

 private int _configType;
 public   int ConfigType
 {
  get
  {
   return _configType;
  }
  set
  {
   _configType=value;
  }
 }

 public bool SetValue(string key, string value)
 {
  XmlDocument cfgDoc = new XmlDocument(); 
  loadConfigDoc(cfgDoc);
   // retrieve the appSettings node 
  node =  cfgDoc.SelectSingleNode("//appSettings");
   
   if( node == null )
   {
    throw new System.InvalidOperationException( "appSettings section not found"); 
   }
   
  try
  {
   // XPath select setting "add" element that contains this key    
   XmlElement addElem= (XmlElement)node.SelectSingleNode("//add[@key='" +key +"']") ;
   if (addElem!=null)
   {
    addElem.SetAttribute("value",value);    
   }
    // not found, so we need to add the element, key and value
   else 
   {
    XmlElement entry = cfgDoc.CreateElement("add");
    entry.SetAttribute("key",key);
    entry.SetAttribute("value",value); 
    node.AppendChild(entry);    
   }
   //save it
   saveConfigDoc(cfgDoc,docName);
   return true;
  }
  catch 
  {
   return false;
  }
 }
 
 private void saveConfigDoc(XmlDocument cfgDoc,string cfgDocPath)
 { 
  try
  {    
   XmlTextWriter writer = new XmlTextWriter( cfgDocPath , null );
   writer.Formatting = Formatting.Indented;     
   cfgDoc.WriteTo( writer );     
   writer.Flush();
   writer.Close();   
   return;
  }
  catch
  {
   throw;
  }
 }
 
 public bool removeElement ( string elementKey)
 {
  try
  {
   XmlDocument cfgDoc = new XmlDocument(); 
   loadConfigDoc(cfgDoc);
   // retrieve the appSettings node 
   node =  cfgDoc.SelectSingleNode("//appSettings");   
   if( node == null )
   {
    throw new System.InvalidOperationException( "appSettings section not found"); 
   }   
   // XPath select setting "add" element that contains this key to remove   
   node.RemoveChild( node.SelectSingleNode("//add[@key='" +elementKey +"']") );
   
   saveConfigDoc(cfgDoc,docName);
   return true;
  }
  catch
  {
   return false;
  }
 }


 private XmlDocument loadConfigDoc( XmlDocument cfgDoc )
 { 
  // load the config file 
  if(  Convert.ToInt32(ConfigType)==Convert.ToInt32(ConfigFileType.AppConfig))
  {
    
   docName= ((Assembly.GetEntryAssembly()).GetName()).Name; 
   docName +=   ".exe.config";
  }
  else
  {
   docName=System.Web.HttpContext.Current.Server.MapPath("web.config");
  }
  cfgDoc.Load( docName ); 
  return cfgDoc;
 }

}