c# - XMLDocument GetElementByID returning null

I'm trying to get an element of a xml by using the function GetElementById, but the function is always returning null.

//get xml text from a web service
string xml = aS.createTree();
XmlDocument tree = new XmlDocument();
tree.LoadXml(xml);

//get all nodes with the tag name "item"
XmlNodeList node = tree.GetElementsByTagName("item");

//just for test to see if i could get the attribute value which returns the expected
string idTemp = node[0].Attributes["ID"].Value;
XmlElement elem = tree.GetElementById("1");

elem is always returning null. Can you guys help me out?

By the way this is the xml that i'm trying to parse:

   
   
   
]>

   
       
   
   

       
       
           
               
                   
               
           
           
       
   

Answer

As far as I know the id att cannot start with a number. Can you try some thing like id="_1" and see how it works.