Question

I am writing a prgm that via the ADO datacontext, I am running a query on the database that uses a group clase and returns an xml document. I am able to get the xml to work, but the XAttribute("pub_id", from p in g select new { p.Pubs_id }) is giving :

System.Linq.Enumerable+WhereSelectEnumerableIterator`2[Pubs.BookStore+BookResults,<>f__AnonymousType1`1[System.String]]

below is the code:

XDocument xdoc = new XDocument(new XElement("reports",
 from b in bookResults 
 group b by b.Title1 into g 
 select new XElement("book", 
     new XAttribute("pub_id", from p in g select new { p.Pubs_id }), 
     new XElement("Title", g.Key), 
     from bk in g 
     select new XElement("Name", new XAttribute("au_id", bk.Au_id), bk.Name)) 
 ) 

xdoc.Save("Books.xml");    

sample xml output desired ( using pubs sample db)

<reports>
  <book pub_id="1389">
    <Title>The Busy Executive's Database Guide</Title>
    <Name au_id="409-56-7008">Bennet,Abraham</Name>
    <Name au_id="213-46-8915">Green,Marjorie</Name>
  </book>
  <book pub_id="0877">
    <Title>Fifty Years in Buckingham Palace Kitchens</Title>
    <Name au_id="648-92-1872">Blotchet-Halls,Reginald</Name>
  </book>
  <book pub_id="0877">
    <Title>The Gourmet Microwave</Title>
    <Name au_id="722-51-5454">DeFrance,Michel</Name>
    <Name au_id="899-46-2035">Ringer,Anne</Name>
  </book>

Answer 1

You’re providing a query returning a sequence as the value of an attribute. My guess is that you expect there to be a single result, in which case you just need to change it to:

new XAttribute("pub_id", (from p in g select new { p.Pubs_id }).Single())

Or even:

new XAttribute("pub_id", (from p in g select p.Pubs_id).Single())

It’s not really clear whether that is what you’re expecting though – but that’s the problem. LINQ to XML is calling ToString on your query, and you’re seeing the result of that. Change the second constructor argument to something which gives a single value, however you need to do it.

I suspect you’ll find that if you indent your code more clearly, it’ll make it more obvious what’s going on – at the moment it’s not really clear just from looking at it. I would rewrite your query as provided in the question as:

 from b in bookResults
 group b by b.Title1 into g
 select new XElement("book",
     new XAttribute("pub_id", from p in g select new { p.Pubs_id }),
     new XElement("Title", g.Key),
     from bk in g
     select new XElement("Name", new XAttribute("au_id", bk.Au_id), bk.Name))
 )