NullReferenceException adding XElement To An XDocument

Question

I'm trying to add dynamically elements to a root using LINQ, it was working before. But it returns "Object reference not set to an instance of an object.". It only works creating the new XElement instance manually.

try  
{
   XDocument xdoc = XDocument.Load(_documentName);
   XElement _newElements = new XElement(_rowName);

   foreach(string s in _commaSeparatedNameValues)
   {
       _newElements.Add(new XElement( s.Split(',')[0], s.Split(',')[1]));
   }

   xdoc.Element(_rowName).Add(_newElements);
   xdoc.Save(_documentName);
}
catch(Exception ex)
{
   string s = ex.Message;
}

Which line gets the exception? And don't use try/catch that way - it hides errors. — John Saunders, Jun 05 '14 at 20:02
Catch the exception and look at the stack trace to find out which line actually threw the exception. Then inspect that line and find out why something is null on that line at any given point in the program. — dodexahedron, Jun 05 '14 at 20:06
xdoc.Element(_rowName).Add(_newElements); it doesnt return null objec — Witcacy Martinez, Jun 05 '14 at 20:43

H H · Accepted Answer · 2014-06-05T21:53:38.640

1

XDocument xdoc = XDocument.Load(_documentName);       
XElement _newElements = new XElement(_rowName);
...
xdoc.Element(_rowName).Add(_newElements);

You never add _newElements to xdoc, so xdoc.Element(_rowName) will be null.
And otherwiser it would have been an attempt to add an element to itself.

The fix, untested:

//xdoc.Element(_rowName).Add(_newElements);
xdoc.Add(_newElements);

or more probably:

xdoc.Root.Add(_newElements);

edited Jun 05 '14 at 21:53

answered Jun 05 '14 at 20:16

H H

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Well, manually it works int his way: XElement _newElements = new XElement(_rowName, new Xelement...); but in my current scenario i must do it dinamically... – Witcacy Martinez Jun 05 '14 at 20:52
Thanks for the answer, but i have to build the xml dynamically. May be the question is other. I understand. – Witcacy Martinez Jun 05 '14 at 21:37
xdoc.Root.Add(_newElements); It works! Thanks i spent 4 hours, im newbie using linq and xml. :D – Witcacy Martinez Jun 05 '14 at 22:02

NullReferenceException adding XElement To An XDocument

1 Answers1