读取XML时在LINQ中正确使用null条件运算符

using System;
using System.Linq;
using System.Xml.Linq;

public class Program
{
    public static void Main()
    {
        // 加载XML文档
        XDocument doc = XDocument.Load("example.xml");

        // 查询单个元素并使用null条件运算符访问属性
        XElement element = doc.Descendants("Book")
            .FirstOrDefault(b => (string)b.Element("Title") == "LINQ in Action");

        string author = element?.Element("Author")?.Value;
        Console.WriteLine("Author: " + author);

        // 查询多个元素并使用null条件运算符访问属性
        var books = doc.Descendants("Book")
            .Where(b => (int)b.Element("Price") > 20)
            .Select(b => new
            {
                Title = b.Element("Title")?.Value,
                Price = (decimal?)b.Element("Price")
            });

        foreach (var book in books)
        {
            Console.WriteLine("Title: " + book.Title);
            Console.WriteLine("Price: " + book.Price);
        }
    }
}

<Books>
  <Book>
    <Title>LINQ in Action</Title>
    <Author>Joe Albahari</Author>
    <Price>30.00</Price>
  </Book>
  <Book>
    <Title>Pro LINQ: Language Integrated Query in C# 2010</Title>
    <Author>Joseph C. Rattz</Author>
    <Price>25.50</Price>
  </Book>
</Books>