Linq to XML - Null Reference Exception when using linq query.n

Question

I have a simple XML file:

<?xml version="1.0" encoding="utf-8"?>
<ConvenioValidacao>
    <convenio ven_codigo="1" tipoValidacao="CPF"></convenio>
    <convenio ven_codigo="1" tipoValidacao="MATRICULA"></convenio>
    <convenio ven_codigo="3" tipoValidacao="CPF"></convenio>
    <convenio ven_codigo="4" tipoValidacao="CPF"></convenio>
</ConvenioValidacao>

I'm trying to do a simple query against this xml file using Linq to XML, here is what i'm doing:

var myXmlDoc = XElement.Load(filePath);
var result =  from convenio in myXmlDoc.Element("ConvenioValidacao").Elements("convenio")
                 where (string)convenio.Attribute("ven_codigo") == "1" &&
                 (string)convenio.Attribute("tipoValidacao") == "CPF"
                 select convenio;

It is not working, I'm getting null reference exception.

What I'm doing wrong?

Andrew Hare · Accepted Answer · 2009-08-25 15:10:35Z

9

Use this instead:

var result = from convenio in myXmlDoc.Elements("convenio")
                 where (string)convenio.Attribute("ven_codigo") == "1" &&
                 (string)convenio.Attribute("tipoValidacao") == "CPF"
                 select convenio;

Since myXmlDoc is of type XElement there is no "document element" and as such the root of the element is the root node (<ConveioValidacao>). Since this is the root node you don't need to specify it in an Elements method since that is current position in document.

As a side note, I recommend that you rename myXmlDoc to myXmlElement to reduce confusion.

answered Aug 25, 2009 at 15:10

Andrew Hare

353k75 gold badges649 silver badges642 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

zer0w1dthspace · Accepted Answer · 2009-08-25 15:15:02Z

1

.Element method gets first child element of the given element, in here ConveioValidacao is not a child element, it is the parent element, when you load by XEelemnt.Load() method it gets ConveioValidacao and it's child elements, so u should use Andrew's code.

answered Aug 25, 2009 at 15:15

zer0w1dthspace

1,0522 gold badges17 silver badges34 bronze badges

Comments

David Basarab · Accepted Answer · 2009-08-25 15:09:48Z

0

Try Descendants instead of Elements

var result =  from convenio in myXmlDoc.Descendants("ConveioValidacao").Descendants("convenio")
                 where (string)convenio.Attribute("ven_codigo") == "1" &&
                 (string)convenio.Attribute("tipoValidacao") == "CPF"
                 select convenio;

answered Aug 25, 2009 at 15:09

David Basarab

73.4k43 gold badges131 silver badges158 bronze badges

1 Comment

Andrew Hare Over a year ago

That stops it from throwing an exception but it doesn't solve the problem. myXmlDoc is an XElement not an XDocument which means that the <ConveioValidacao> node is not a descendant of it.

Collectives™ on Stack Overflow

Linq to XML - Null Reference Exception when using linq query.n

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related