title: what does the error "System.Xml.Linq.XDocument' does not contain a def" mean?
body: <p>I'm trying to write a code to convert a xml file into a datatable.
  I'm getting this below error </p>
  
  <p>System.Xml.Linq.XDocument' does not contain a definition for 'DocumentNode' and no extension method 'DocumentNode' accepting a first argument of type 'System.Xml.Linq.XDocument' could be found (are you missing a using directive or an assembly reference?)</p>
  
  <p>What am I missing?</p>
  
  <p>Below is my code</p>
  
  <pre><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Text;
  using System.IO;
  using System.Xml.XPath;
  
  using System.Xml.Linq;
  
  namespace ConsoleApplication1
  {
      class Program
      {
          static void Main()
          {
  
  
  
              var xdoc = System.Xml.Linq.XDocument.Load(filename);
              System.Xml.XmlElement xelRoot = xdoc.DocumentElement;
              System.Xml.XmlNodeList xList = xelRoot.SelectNodes("/rulebase/security/rules/entry");
  
              int x = 0;
              int y = 0;
              string[] ColumnArray = new string[25];
              string[] RowArray = new string[25];
  
  
              foreach (System.Xml.XmlNode pNode in xList)
              {
  
  
  
                  if (pNode.ChildNodes.Count = 0)
                  {
  
                  }
                  else
                  {
                      string val1 = "";
                      string nodeVal = "";
  
                      string nodeName = pNode.name;
                      foreach (System.Xml.XmlNode childNode in pNode.ChildNodes)
                      {
                          val1 = val1 + childNode.value + ", ";
                      }
                      val1 = val1 + " ,";
                      nodeVal = val1.substring(0, val1.length - 3);
  
                      ColumnArray[x] = nodeName;
                      RowArray[y] = nodeVal;
                      x++;
                      y++;
  
                  }
              }
  
              System.Data.DataTable table1 = new System.Data.DataTable("entry");
  
              foreach (string s in ColumnArray)
              {
                  table1.Columns.Add(s);
              }
  
              System.Data.DataRow row;
              row = table1.LoadDataRow(RowArray, true);
          }
  
      }
  }
  </code></pre>