LINQ to XML: Difficulty Filtering Elements Based on Nested Attribute Values in C#
I'm maintaining legacy code that I'm getting frustrated with Does anyone know how to I've been working with LINQ to XML in C# and working with issues when trying to filter elements based on nested attribute values. I have an XML structure that looks like this: ```xml <Books> <Book id="1"> <Title>Introduction to LINQ</Title> <Author> <Name>John Doe</Name> <Country>USA</Country> </Author> </Book> <Book id="2"> <Title>Advanced LINQ</Title> <Author> <Name>Jane Smith</Name> <Country>Canada</Country> </Author> </Book> </Books> ``` I am trying to filter the books by `Author.Country`, specifically to find all books authored by someone from the USA. My LINQ query looks like this: ```csharp XDocument xmlDoc = XDocument.Load("books.xml"); var usaBooks = from book in xmlDoc.Descendants("Book") where (string)book.Element("Author")?.Element("Country") == "USA" select book; ``` However, I'm getting a `NullReferenceException` if a `Book` element does not have an `Author` or a `Country`. I tried adding additional null checks, but it still fails: ```csharp var usaBooks = from book in xmlDoc.Descendants("Book") where book.Element("Author") != null && book.Element("Author")?.Element("Country") != null && (string)book.Element("Author")?.Element("Country") == "USA" select book; ``` I thought using the null-conditional operator would handle this, but the exception still occurs when trying to access the `Country` element. Can anyone guide to understand how to avoid this scenario and correctly filter based on nested attributes? Also, is there a more efficient way to handle this filtering in LINQ? Any insights or alternative approaches would be greatly appreciated! Thanks in advance! This is for a CLI tool running on Linux. Any ideas how to fix this? Is there a simpler solution I'm overlooking?