Nullreference exception in linq to xml

You can alway test for null on a XElement.

var result = from book in books.Elements("book")
             where book.Attribute("id") != null && book.Attribute("name") != null
             select new { Name = book.Attribute("name").Value, ISBN = book.Attribute("isbn") == null ? "Missing" : book.Attribute("isbn").Value };

If attribute "isbn" is missing, the string "Missing" is used.

You're trying to call method or property on the class instance which was never initialized or explicitly set to null. That's all. I can be anywhere.

Did you run it under Debugger. It would show you exact line of code where it happens. If you still cannot figure out how to fix the problem, post a relevant part of code; don't forget to indicate the lines of code responsible for exception with full exception information.

—SA