getnodebyxpath throws nullreferenceexception

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Aximili 177 posts 278 karma points

Jun 02, 2015 @ 12:52

XSLT

I'm working on a project using Umbraco 6 and WebForms.

In Content, there are Employees. So umbraco.config contains these lines:

  <Employee id="15853" ...>
    <email>xxx</email>
  </Employee>

In C#, how do I get the Employee node having email=xxx? I tried this:

Node nodeEmail = Node.GetNodeByXpath("//Member/email[text()='xxx']");

and it throws this exception:

[NullReferenceException: Object reference not set to an instance of an object.]
   umbraco.NodeFactory.Node.initialize() +172
   umbraco.NodeFactory.Node..ctor(XmlNode NodeXmlNode) +179
   umbraco.NodeFactory.Node.GetNodeByXpath(String xpath) +168

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Chriztian Steinmeier 2798 posts 8788 karma points MVP 7x admin c-trib

Jun 02, 2015 @ 12:56
0
Hi Hardi,

In the XPath expression you need to use the document type's alias (i.e. "Employee") - so if it's <Employee> in the XML, it should be Employee in the expression, i.e.:
```
Node nodeEmail = Node.GetNodeByXpath("//Employee/email[. = 'xxx']");
```
/Chriztian
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Aximili 177 posts 278 karma points

Jun 02, 2015 @ 15:20
0
Oh I'm sorry I cut and pasted the wrong thing. I can't edit it anymore.

It was already Employee. But it throws a NullReferenceException.

These lines are fine:
```
Node nodeEmail = Node.GetNodeByXpath("//Employees");
```
```
Node nodeEmail = Node.GetNodeByXpath("//Employees/Employee");
```
```
Node nodeEmail = Node.GetNodeByXpath("//Employee");
```
But this throws NullReferenceException
```
Node nodeEmail = Node.GetNodeByXpath("//Employees/Employee/email");
```
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Sebastian Dammark 581 posts 1385 karma points

Jun 02, 2015 @ 18:52
2
Try this:
```
Node nodeEmail = Node.GetNodeByXpath("//Employee[email = 'xxx']");
```
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Aximili 177 posts 278 karma points

Jun 03, 2015 @ 14:08

0

It works! Thank you Sebastian!

I still don't understand why the other queries were throwing the exception, even though they were fine when tested on XPath testers. But thanks!

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Chriztian Steinmeier 2798 posts 8788 karma points MVP 7x admin c-trib

Jun 03, 2015 @ 14:17

1

Hi Hardi,

The error you get is because the code that deals with an umbraco Node, and all of the working XPath expressions return a node - the ones throwing an error, selects a property instead. I didn't catch that your code was using a node (the "nodeEmail" name threw me off, I guess :-). Sebastian's XPath selects the <Employee> node that has an <email> equal to 'xxx', whereas mine selected the actual <email> element. Subtle difference - but if your C# code expects a Node, the error message makes perfect sense.

Does that help understanding?

/Chriztian

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Aximili 177 posts 278 karma points

Jun 04, 2015 @ 01:47

0

Ah of course! I was concentrating too much on the XML I forgot about the Node itself! Thank you Chriztian :)

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