Question

I trying to get all attribute values from xml file where value doesn’t start with some text

i have this code

IEnumerable<XElement> elements =
    (from el in xmlFile.Root.Elements(elementName)
     where (string)el.Attribute(attributeName)  !StartWith("abc")
     select el);

How can i fix this

Answer 1

You need to use a valid expression, e.g.

where !el.Attribute(attributeName).Value.StartsWith("abc")

It’s important to understand that what goes into a LINQ where clause isn’t “magic” syntax – it’s just a normal expression, which can use the range variables declared by the query expression (el in this case). So you should have asked yourself, “If I were writing this not in LINQ, and I had a variable called el referring to an element, how would I have written an if condition to check that the attribute value didn’t start with abc?”

(I use the explicit conversion when the attribute can be missing and I want to just get a null, but in this case you’re going to go bang when the attribute’s missing anyway, and you just want the string value, so you might as well use the Value property.)

Note that as you’ve only got a where clause here (and a trivial select) it would probably be more readable to use the non-query-expression form:

var elements = xmlFile.Root.Elements(elementName)
                      .Where(el => !el.Attribute(attributeName).Value.StartsWith("abc"));