.NET中如何使用LINQ to XML操作XML

XElement books = new XElement("Books",
    new XElement("Book",
        new XAttribute("Id", "1"),
        new XElement("Title", "C# 编程指南"),
        new XElement("Author", "张三")
    ),
    new XElement("Book",
        new XAttribute("Id", "2"),
        new XElement("Title", "深入理解 LINQ"),
        new XElement("Author", "李四")
    )
);

var query = from book in books.Elements("Book")
            where (string)book.Element("Author") == "张三"
            select (string)book.Element("Title");
<p>foreach (string title in query)
{
Console.WriteLine(title);
}

var titles = books.Elements("Book")
                   .Where(b => b.Element("Author")?.Value == "张三")
                   .Select(b => b.Element("Title")?.Value);

var firstBook = books.Elements("Book").First();
firstBook.Add(new XElement("Pages", 500));

XElement loadedBooks = XElement.Load("books.xml");

books.Save("output.xml");