System.Xml.XPath.XPathNavigator.CreateAttribute C# (CSharp) Method

        public virtual void CreateAttribute(string prefix, string localName, string namespaceURI, string value)
        {
            XmlWriter writer = CreateAttributes();
            writer.WriteStartAttribute(prefix, localName, namespaceURI);
            if (value != null)
            {
                writer.WriteString(value);
            }
            writer.WriteEndAttribute();
            writer.Close();
        }

 public static void SetOrCreateXmlAttribute(XPathNavigator node, string localName, string namespaceURI, string value)
 {
     if (node.MoveToAttribute(localName, namespaceURI))
     {
         node.SetValue(value);
         node.MoveToParent();
     }
     else
     {
         node.CreateAttribute("", localName, namespaceURI, value);
     }
 }