expression must evaluate to a node set while using xpath

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Phong Nguyen Dinh 26 posts 197 karma points

Nov 02, 2016 @ 04:37

Expression must evaluate to a node-set while using XPath

I am getting error while trying to get nodes by XPath. Any help is appreciated.

var xpathQuery = string.Format("//{0}/[@nodeName='{1}']/{2}//[@nodeTypeAlias='{3}' or @nodeTypeAlias='{4}']",
                DocumentTypes.Kempinski,
                language.ToLower(),
                DocumentTypes.CorporatePressReleasesLandingPage,
                DocumentTypes.TemplateAContentWithTextOnly,
                DocumentTypes.TemplateBContentWithFeaturedImage);

I use glass mapper for DocumentTypes. Here is my umbraco backend structure:

<Kempinski>
    <en name="en">
        <CorporatePressReleasesLandingPage>

            <TemplateAContentWithTextOnly>
            </TemplateAContentWithTextOnly>

            <TemplateBContentWithFeaturedImage>
            </TemplateBContentWithFeaturedImage>

        </CorporatePressReleasesLandingPage>
    </en>
</Kempinski>

I want to take all Nodes with Document Types have alias "TemplateAContentWithTextOnly" and "TemplateBContentWithFeaturedImage"

enter image description here

And i get this error. Anyone have any idea?

Regard,

Phong.

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Dave Woestenborghs 3504 posts 12135 karma points MVP 9x admin c-trib

Nov 02, 2016 @ 07:12

0

Hi Phong,

Don't immediatly see what is wrong with the query, but I'm no xpath expert.

What I would do is simplify the query and bits.

So I would start getting the Kempinskie part first. Than the language node...and so on.

That way you can find the part of the query that breaks.

Dave

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Phong Nguyen Dinh 26 posts 197 karma points

Nov 02, 2016 @ 07:53

0

Hi Dave,

Thank for your advice.

I did exactly what you said to me but every single time i tried to get a node, it was always null, even the first one: Kempinski.

And i get more confused about this. Do you have any idea Dave?

Phong.

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Dave Woestenborghs 3504 posts 12135 karma points MVP 9x admin c-trib

Nov 02, 2016 @ 08:26
0
Hi Phong,

The xml you posted is from the umbraco.config file in the App_Data folder ?

I tested this query and this works on the supplied xml fragment :
```
//Kempinski/*[@nodeName='en']/CorporatePressReleasesLandingPage/*[self::TemplateAContentWithTextOnly or self::TemplateBContentWithFeaturedImage]
```
Dave
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Chriztian Steinmeier 2800 posts 8791 karma points MVP 8x admin c-trib

Nov 02, 2016 @ 08:29
1
Hi Phong,

There's a couple of tiny bugs in the XPath - try this instead:
```
string.Format("//{0}[@nodeName='{1}']/{2}//*[@nodeTypeAlias='{3}' or @nodeTypeAlias='{4}']"
```
Notice that there needs to be a "path step" (e.g. *, elementname or similar) before a predicate (thing in square brackets).

Another version could be this:
```
string.Format("//{0}[@nodeName='{1}']/{2}//*[self::{3} or self::{4}]"
```
(I like that better, but it may not be as obvious if you're not familiar with XPath)

Hope that helps,

/Chriztian
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Phong Nguyen Dinh 26 posts 197 karma points

Nov 02, 2016 @ 10:34
100
Thank you so much Dave and Chriztian for your help, i found a solution.

I change my string format to:
```
string.Format("//{0}/*[@nodeName='{1}']/{2}/*[local-name()='{3}' or local-name()='{4}']"
```
I also tried your ideas but it didn't work, so sorry for my late reply.

It took me a lot of time but i think i get better with XPath now.

Thank you guys again for your kindness. Love this comunity.

Regard, Phong.
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