Here is an example of adding an attribute to an XmlDocument in C# and .Net. The below code reads in Xml. Where there are nodes that do not contain and ID attribute, we will add that attribute using the name as the value.

   1: public static string xmlAcct =

   2: @"<?xml version='1.0' encoding='utf-8'?>

   3: <Accounts>

   4: <acct acct='aex113' country_code='us' name='abcde' />

   5: <acct acct='aex114' name='eeaad' country_code='us' />

   6: <acct acct='aex115' country_code='us' name='eoo' id='eoo9' />

   7: </Accounts>

   8: ";

   9:

  10: public static void AddAttribute()

  11: {

  12:

  13:     XmlDocument originalXml = new XmlDocument();

  14:

  15:

  16:     originalXml.LoadXml(xmlAcct);

  17:

  18:     XmlNodeList accts

  19:        = originalXml.SelectNodes("descendant::*[name(.) ='acct']");

  20:     XmlNode temp;

  21:     XmlNode name;

  22:     XmlAttribute attr;

  23:

  24:     foreach (XmlNode current in accts)

  25:     {

  26:         temp = current.SelectSingleNode("@id");

  27:         if (temp == null)

  28:         {

  29:             name = current.SelectSingleNode("@name");

  30:             if (name != null)

  31:             {

  32:                 attr = originalXml.CreateAttribute("id");

  33:                 attr.InnerText = name.InnerText;

  34:                 current.Attributes.Append(attr);

  35:             }

  36:         }

  37:

  38:     }

  39:

  40:     Console.WriteLine(originalXml.OuterXml);

  41:

  42:

  43: }

• Line 01: Create Test XMl
• Line 16: Load the test Xml.
• Line 19: Get all the account nodes using Xpath.
• Line 24: Work through each account node to add an attribute if ID does not exist.
• Line 27: When null we need to add the ID node.
• Line 29: We will use the name as the ID.
• Line 32: We have to create the attribute off of the current node. Very important, for we can’t just slap any old node on. It has to be from the current branch/node.
• Line 40: Display the changes.

Tags: Document Object Model, XMLDocument

This is a quick example of loading data into and XmlDocument and then extracting data using XPath. Each of those topics have books written on them and one can surely use this sample as a starting point for that learning.

Note the Xpath used does not demonstate the full capabilities of Xpath such as one can extract attributes off of nodes using the @ sign.

   1: XmlDocument xd = new XmlDocument();

   2:

   3: xd.LoadXml(

   4: @"<?xml version='1.0'?>

   5:     <Wrapper>

   6:         <myData>some stuff</myData>

   7:         <level access='t'>4</level>

   8:         <size>medium</size>

   9:    </Wrapper>");

  10:

  11: XmlNode node

  12:     = xd.SelectSingleNode(

  13:         "descendant::*[name(.) ='myData']");

  14:

  15: Console.WriteLine("Inner Text ({0}) Outer Xml {1}",

  16:                   node.InnerText,

  17:                   node.OuterXml);

  18:

• Line 1 Create a new XmlDocument.
• Line 3 Load the Xml from a string, other ways one could load from a file.
• Line 11-13 We are interested in getting the first node encountered thats name is myData. By using the SelectSingleNode we can get just one.
• Line 13 This is a generic Xpath that I like to use which can get information from the current node looked being looked at. What it is saying is,Looking at all the decendants of the current node, give me the node where the name found is myData.
• Line 15 We are not checking to see if node is null. In normal code this is a no-no, check before usage!
• Line 16 The actual data is store in the InnerText of the node, which we will extract.
• Line 17 Sometimes we need the xml along with it, see below.

This is what the output looks like:

Inner Text (some stuff) Outer Xml <myData>some stuff</myData>

Tags: Document Object Model, XMLDocument