hi friends

U can use xmlpathdocument and update this is the one way vch u can do

if(!Page.IsPostBack){
        XmlDocument xmlDoc = new XmlDocument();
        xmlDoc.Load(Server.MapPath("categories.xml"));

        XmlNodeList nodeList = xmlDoc.SelectNodes("/CategoryList/Category[@ID='01']");

        // update MainCategory 
        nodeList[0].ChildNodes[0].InnerText = "ASP.NET";
        // update Description 
        nodeList[0].ChildNodes[1].InnerText = "This is now my ASP.NET list.";
        // update Active 
        nodeList[0].ChildNodes[2].InnerText = "false";

        // Don't forget to save the file
        xmlDoc.Save(Server.MapPath("categories.xml"));
        Response.Write("XML File updated!");
    }