c# 读取web.config（xml）文件并进行修改

web config 配置如下:

 　　　　　　　　<add key="ewnhUrl" value="192.168.0.1" />

　　
读取文件并修改

  XmlDocument xml = new XmlDocument();
    //路径
    var ConfigPathew = rootPath + "\dddl\Configs\system.config";
        xml.Load(ConfigPathew);
        XmlNodeList nodesew = xml.GetElementsByTagName("add");
        for (int i = 0; i < nodesew.Count; i++)
          {
             XmlAttribute attew = nodesew[i].Attributes["value"];
             if (attew != null)
               {                                        
                  if (nodesew[i].Attributes[0].Value == "ewnhUrl")
                     {
                       attew = nodesew[i].Attributes["value"];
　　　　　　　　　　　　　　//要写入的文本
                       attew.Value = ExtranetIp.Text + ":" + port;
                        break;
                      }
               }
          }
                     xml.Save(ConfigPathew);

　　//为当前文件夹赋予everyone权限
　　string rootPath = Directory.GetCurrentDirectory();
　　DirectorySecurity fsec = new DirectorySecurity();
　　fsec.AddAccessRule(new FileSystemAccessRule("Everyone", FileSystemRights.FullControl,
　　InheritanceFlags.ContainerInherit | InheritanceFlags.ObjectInherit, PropagationFlags.None, AccessControlType.Allow));
　　System.IO.Directory.SetAccessControl(rootPath, fsec);