Add to XDocument

using System;//from   j  a v a 2  s  .c o  m
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Linq;
using System.IO;


public class MainClass{

   public static void Main(string[] args){   
      XDocument NewDoc = new XDocument(new XDeclaration("1.0", "utf-8", "yes"),
            new XElement("Root", "MyDoc"));  
      NewDoc.AddFirst(new XDocumentType(
               "MyDocType", "MyPubID", 
               "MySysID", "ThisInternalSubset"));


   }
}

using System;//from   ja v  a2  s.  c  o m
using System.Data;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Linq;
using System.IO;


public class MainClass{

   public static void Main(string[] args){   
      XDocument NewDoc = new XDocument(
            new XDeclaration("1.0", "utf-8", "yes"),
            new XElement("Root", "MyDoc"));  
      // Add the CData.
      NewDoc.Element("Root").Add(
            new XElement("CDataElement",
               new XCData("This is a CData Entry!")));

   }
}