Using Linq to query XML by attribute rather than by element?

Question

I currently have the following XML which I'm trying to remove a record from:

<?xml version="1.0" encoding="utf-8"?>
<Photos>
  <Photo UID="7e74a528a5324feb8ed3d7902c8b6a42">
    <Date>2014-08-22T10:22:00.761873+01:00</Date>
    <File>7e74a528a5324feb8ed3d7902c8b6a42.jpg</File>
    <CrimeRef>CR999999/99</CrimeRef>
  </Photo>
  <Photo UID="70c4b3bb2cc54780b49cf10228f472da">
    <Date>2014-08-22T10:49:41.737873+01:00</Date>
    <File>70c4b3bb2cc54780b49cf10228f472da.jpg</File>
    <CrimeRef>CR999999/99</CrimeRef>
  </Photo>
</Photos>

Previously, I was removing records by search for the file name using the following code which worked fine:

public void Delete(string ID)
{
    XDocument xml = XDocument.Load(xmlPath);

    xml.Descendants("Photos")
            .Where(e => (string)e.Attribute("File") == ID)
            .Remove();
}

However, I've just started populating the UID on the Photo element to get around routing issues, so I'd like to remove the files now by the UID value.

I've tried looping through the "Photo" descendants but unfortunately it's just skipping over the element that matches the UID (because, for some reason it isn't matching)

public void Delete(string ID)
{
    XDocument xml = XDocument.Load(xmlPath);

    xml.Descendants("Photo")
            .Where(e => (string)e.Attribute("UID") == ID)
            .Remove();
}

From the debug information, it should match:

enter image description here

Any suggestions would be very welcome, thank you.

.Where(e => (string)e.Attribute("UID").Value == ID)

Lotok
– Lotok

2014-08-22 10:23:41 +00:00
Commented Aug 22, 2014 at 10:23 — Lotok
– Lotok, Commented Aug 22, 2014 at 10:23

Lotok · Accepted Answer · 2014-08-22 10:26:01Z

1

You just forgot to check for the attribute value. If you add .Value this will fix it.

public void Delete(string ID)
{
    XDocument xml = XDocument.Load(xmlPath);

    xml.Descendants("Photo")
            .Where(e => e.Attribute("UID") != null && (string)e.Attribute("UID").Value == ID)
            .Remove();
}

answered Aug 22, 2014 at 10:26

Lotok

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3 Comments

Nick Over a year ago

Thank you very much James, I've just tested this, but when the first element doesn't match I get a System.NullReferenceException error.

Lotok Over a year ago

Updated to include the null check

Nick Over a year ago

You're a star, thank you so much - thinking about it this wouldn't have been an issue if I'd populated the UID from the start like I should have done. Sigh. Thanks again :)

mashet · Accepted Answer · 2014-08-22 10:26:25Z

0

Use Value property:

doc.Descendants().Where(e => (string) e.Attribute("UID").Value == ID).Remove();

answered Aug 22, 2014 at 10:26

mashet

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