Question

Me again… I have an XML File that contains different categories which I would like to query for different attributes.

        <item>                   <title>Industries</title>                   <category type='Channel'>Automotive</category>                   <category type='Type'>Cars</category>                   <category type='Token'>Article</category>                   <category type='SpecialToken'>News</category>                   <guid>637f0dd7-57a0-4001-8272-f0fba60feba1</guid>         </item> 

IN SQL I would write something like.

select * from articles where channel = 'Automative' AND type = 'Cars' etc. etc. 

How can I achieve this with linq? I tried the following query but it returns null. If I combine the two attributes with the ‘OR’ || operator I would get the results, but with all double results if an item matches both criteria.

var articleList = (from item in doc.Descendants('item')                           from _category in item.Elements('category')                          where _category.Value == valueCboChannel && _category.Attribute('domain').Value == 'Channel'                          && (_category.Value == valueCboSubChannel && _category.Attribute('domain').Value == 'SubChannel')                           select new                          {                               Title = item.Element('title').Value,                              Guid= item.Element('guid').Value,                              description = item.Element('description').Value,                              link = item.Element('link').Value                          }).ToList();              ListView1.DataSource = articleList;             ListView1.DataBind();                

Answer 1

I’d simplify it with an extension method to do the tricky lookup:

(updated 12/02/09 to exclude empty elements)

static string CategoryValue(this XElement element, string type) {     var category = element.Elements('category').FirstOrDefault(         c => (string)c.Attribute('type') == type             && !string.IsNullOrEmpty(c.Value)); // UPDATE HERE     return category == null ? null : category.Value; }  static void Main() {     XDocument doc = XDocument.Parse(xml);     var qry = from item in doc.Descendants('item')               where item.CategoryValue('Channel') == 'Automotive'               && item.CategoryValue('Type') == 'Cars'               select item;     foreach (var node in qry)     {         Console.WriteLine(node.Element('guid').Value);     } }