C#

XmlTextReader xmlReader = new XmlTextReader(Application.StartupPath + "\\doc.xml");
            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.Load(xmlReader);
            xmlReader.Close();

            string xpath = string.Format("/StudentRecords/Student");
            XmlNamespaceManager nsmgr = new XmlNamespaceManager(xmlDoc.NameTable);
            XmlNodeList fieldNodes = xmlDoc.SelectNodes(xpath, nsmgr);
            string refName = "";
            int index = 0;
            XmlAttributeCollection ddd;
            XmlNode refNode = null;
            string studentID;
            foreach (XmlNode node in fieldNodes)
            {
                ddd = fieldNodes[index].Attributes;
                studentID = ddd["ID"].Value.ToString();
                
                if (Convert.ToInt32(studentID) == 101)
                {
                    refNode = node.SelectSingleNode("StudentSubject");
                }
            }
            XmlDocument xmldoc = new XmlDocument();
            XmlElement newcatalogentry = xmldoc.CreateElement("StudentMarks");
            XmlAttribute newcatalogattr = xmldoc.CreateAttribute("Total");

            newcatalogattr.Value = "100";

            // Attach the attribute to the XML element
            newcatalogentry.SetAttributeNode(newcatalogattr);



            // New XML element inserted into the document
            xmlDoc.DocumentElement.InsertAfter(newcatalogentry, refNode);
            string path = "C:\\test.xml";
            FileStream fsxml = new FileStream(path, FileMode.Truncate,
                                              FileAccess.Write,
                                              FileShare.ReadWrite);
            xmlDoc.Save(path);

XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.Load(Application.StartupPath + "\\doc.xml");

            string xpath = string.Format("/StudentRecords/Student");
            XmlNodeList fieldNodes = xmlDoc.SelectNodes(xpath);

            XmlNode studentNode = null;
            XmlNode refNode = null;
            
            foreach (XmlNode node in fieldNodes)
            {
                if (node.Attributes["ID"].Value == "101")
                {
                    studentNode = node;
                    refNode = node.SelectSingleNode("StudentSubject");
                }
            }

            if (studentNode != null && refNode != null)
            {
                XmlElement newcatalogentry = xmlDoc.CreateElement("StudentMarks");
                XmlAttribute newcatalogattr = xmlDoc.CreateAttribute("Total");

                newcatalogattr.Value = "100";

                // Attach the attribute to the XML element
                newcatalogentry.SetAttributeNode(newcatalogattr);

                // New XML element inserted into the document
                studentNode.InsertAfter(newcatalogentry, refNode);

                string path = "C:\\test.xml";
                
                xmlDoc.Save(path);
            }

<StudentClass ref="F_GAMES" />

<StudentClass ref="F_STRENGTH" />

<?xml version="1.0"?>
  <StudentRecords>       
      <Student ID="100">
    <StudentClass id="XA" name="XA" >
      <StudentClass ref="F_HEIGHT" />
      <StudentClass ref="F_WEIGHT" />
      <StudentClass ref="F_STRENGTH" />
      <StudentClass ref="F_LIBRARY" /> 
      <StudentClass ref="F_QUALIFIER" />
    </StudentClass>
  </Student>
  <Student ID="101">
    <StudentClass id="XB" name="XB" >
      <StudentClass ref="F_HEIGHT" />
      <StudentClass ref="F_WEIGHT" />
      <StudentClass ref="F_STRENGTH" />
      <StudentClass ref="F_LIBRARY" />     </StudentClass>
</Student> 
</StudentRecords>  

XmlDocument xmlDoc = new XmlDocument();            
            xmlDoc.Load(Application.StartupPath :-D  + "\\doc.xml");           
            string xpath = string.Format("/StudentRecords/Student");            
            XmlNodeList fieldNodes = xmlDoc.SelectNodes(xpath);            
            XmlNode studentNode = null;            
            XmlNode refNode = null;                        
            foreach (XmlNode node in fieldNodes)            
            {
                if (node.Attributes["ID"].Value == "101")    
                {
                    fieldNodes = xmlDoc.SelectNodes(xpath + "/StudentClass");
                    XmlNode node1 = fieldNodes.Item(0);
                    studentNode = node1;
                    refNode = node1.SelectSingleNode("StudentClass");
                    break;
                }
                       
            }            
            if (studentNode != null && refNode != null)            
            {
                XmlElement newcatalogentry = xmlDoc.CreateElement("StudentClass");
                XmlAttribute newcatalogattr = xmlDoc.CreateAttribute("ref");            
                newcatalogattr.Value = "F_NewCategory";                
                // Attach the attribute to the XML element                
                newcatalogentry.SetAttributeNode(newcatalogattr);                
                // New XML element inserted into the document                
                studentNode.InsertAfter(newcatalogentry, refNode);                
                string path = "C:\\test.xml";                                
                xmlDoc.Save(path);            
            }

foreach (XmlNode node in fieldNodes)
{
    if (node.Attributes["ID"].Value == "101")
    {
        fieldNodes = node.SelectNodes("/StudentClass");

        if (fieldNodes != null && fieldNodes.Count > 0)
        {
            studentNode = fieldNodes.Item(0);

            //loop thrugh all childNodes to get node with ref=F_STRENGTH
            foreach (XmlNode nodeClass in studentNode.ChildNodes)
            {
                if (nodeClass.Attributes["ref"].Value == "F_STRENGTH")
                {
                    refNode = nodeClass;
                    break;
                }
            }
        }
        break;
    }
}

if (fieldNodes != null && fieldNodes.Count > 0)

foreach (XmlNode node in fieldNodes)
{
    if (node.Attributes["ID"].Value == "101")
    {
        studentNode = node["StudentClass"];

        if(studentNode != null)
        {
            //loop thrugh all childNodes to get node with ref=F_STRENGTH
            foreach (XmlNode nodeClass in studentNode.ChildNodes)
            {
                if (nodeClass.Attributes["ref"].Value == "F_STRENGTH")
                {
                    refNode = nodeClass;
                    break;
                }
            }
        }
        break;
    }
}

Anindya Chatterjee wrote:

I am going to create a desktop mail storage