CODEWITHSUNDEEP
c#asp.netxmllinqlinq-to-xml
Steven
Steven

Reputation: 18869

XElement query gives error: "Sequence contains no elements"

I'm trying to query this xml:

<pageMap>
  <pageMapNode id="8039CE09-E7DA-47E1-BCEC-DF96B5E411F4">
    <pageMapNode id="79DC0E8A-82F1-47DF-836E-099665A7D2E3"></pageMapNode>
    <pageMapNode id="3B79FAAC-EB2D-41AC-A91E-12541D0EB377">
      <pageMapNode id="170A9FC3-C03E-4088-AC5E-93AA038E0114"></pageMapNode>
    </pageMapNode>
  </pageMapNode>
  <pageMapNode id="A34CADA7-317D-405C-8E8F-DB113F40407F"></pageMapNode>
</pageMap>

Here's my function:

protected string GetParent(Guid nodeId)
{
    XDocument doc = XDocument.Parse(GetXml());  // parses xml displayed above

    // returns the 5 page map nodes displayed above
    IEnumerable<XElement> nodes = doc.Descendants("pageMapNode");

    // error: "Sequence contains no elements"
    XElement node = doc.Descendants("pageMapNode")
        .Where(n => n.Attribute("id").ToString().ToLower() == 
            nodeId.ToString().ToLower()).Single();

    ...
}

The nodeId parameter I'm passing in is correct - I should get a match, so I don't know why it's returning an error.

Anyone see what I'm doing wrong?

Upvotes: 3

Views: 1498

Answers (1)

Henk Holterman
Henk Holterman

Reputation: 273691

n.Attribute("id") returns an XAttribute, not a string. You need .Value instead of .ToString()

XElement node = doc.Descendants("pageMapNode")
    .Where(n => n.Attribute("id").Value.ToLower() == 
        nodeId.ToString().ToLower()).Single();

and you can shorten it to

XElement node = doc.Descendants("pageMapNode")
    .Single(n => n.Attribute("id").Value.ToLower() == 
        nodeId.ToString().ToLower());

Upvotes: 5

Related Questions