Question

I want to find the Xelement attribute.value which children have a concrete attribute.value.

string fatherName =  xmlNX.Descendants("Assembly")
                           .Where(child => child.Descendants("Component")
                               .Where(name => name.Attribute("name").Value==item))
                           .Select(el => (string)el.Attribute("name").Value); 

How can I get the attribute.value? What does it say that is a bool?

EDITED
Originally I Have the following XML:

<Assembly name="1">
  <Assembly name="44" />
  <Assembly name="3">
     <Component name="2" />
  </Assembly>
  </Assembly>

I need to get the attribute.value where its children (XElement) has an expecific attribute.value
In this example, I would get the string “3” because i am searching the parent of the child which attribute.value == “2”

Answer 1

Because of how the nested Where clauses are written.

The inner clause reads

child.Descendants("Component").Where(name => name.Attribute("name").Value==item)

This expression has a result of type IEnumerable<XElement>, so the outer clause reads

.Where(child => /* an IEnumerable<XElement> */)

However Where expects an argument of type Func<XElement, bool> and here you end up passing in a Func<XElement, IEnumerable<XElement>> — hence the error.

I ‘m not offering a corrected version because your intent is not clear at all from the given code, please update the question accordingly.

Update:

Looks like you want something like this:

xmlNX.Descendants("Assembly")
     // filter assemblies down to those that have a matching component
     .Where(asm => asm.Children("Component")
                     .Any(c => c.name.Attribute("name").Value==item))
     // select each matching assembly's name
     .Select(asm => (string)asm.Attribute("name").Value)
     // and get the first result, or null if the search was unsuccessful
     .FirstOrDefault();