Why doesn't linq to xml recognize my the attributes in my XML file?

Question

I'm brand new to LINQ to XML (comfortable with LINQ to sql) and learning my way around with this tutorial http://www.joe-stevens.com/2010/01/08/linq-to-xml-tutorial/

When I write this linq query

Dim data As XDocument = XDocument.Load(xmlFileLocation)
Dim outputFileLoc = (From c In data.Descendants("Program") Where c.Attribute("ProgramName").Equals("EnviroEpi") Select c)

on this XML file:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Programs>
   <Program ProgramName="EnviroEpi">
      <Type>csv</Type>
      <Location>test</Location>
   </Program>
   <Program ProgramName="Epi">
       <Type>HL7</Type>
       <Location>test</Location>
   </Program>
   <Program ProgramName="Lead">
      <Type>csv</Type>
      <Location>test</Location>
   </Program>
</Programs>

I get an error:

Sequence contains no elements

Does this mean that LINQ can't see the ProgramName attribute of my program nodes? Or am I missing something else? As far as I can tell, I'm doing everything exactly like in the tutorial.

Thanks again for the help. I'm really just getting a feel for LINQ to XML.

Edit

... where c.attribute("ProgramName").Equals("EnviroEpi") // returns no elements. 

This works:

 c.attribute("ProgramName").value.equals("EnviroEpi") //added in .value to get it to work

Answer 1

You don't want Descendants("Programs").Descendants , that would return any descendant of the Programs elements - most of which are unrelated and don't have a ProgramName attribute, hence you get a NullReferenceException .

You also need to use Attribute("ProgramName").value.Equals("EnviroEpi") to get to the value of the program name attribute.

You want Descendants("Program") instead:

 Dim outputFileLoc = (From c In data.Descendants("Program") Where c.Attribute("ProgramName").Equals("EnviroEpi") Select c).First

Answer 2

The issue is most likely that data.Descendants("Programs") or data.Descendants("Programs").Descendants is null. You need to do null checks along the way, you can't really just chain a bunch of objects together like you've done.