LINQ to Enumerable
代码如下
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Linq;
namespace ConsoleApplication1
{
class Program
{
private static void PrintEnumerable<T>(IEnumerable<T> enumerable)
{
foreach (var e in enumerable) Console.WriteLine(e);
Console.WriteLine("==========");
}
static void Main(string[] args)
{
var MyBooks = new BookCollection(){
{100101,"Harry Potter and the Philosopher's Stone"},
{100102,"Harry Potter and the Chamber of Secrets"},
{100103,"Harry Potter and the Prisoner of Azkaban"},
{100104,"Harry Potter and the Goblet of Fire"},
{100105,"Harry Potter and the Order of the Phoenix"},
{100106,"Harry Potter and the Half-Blood Prince"},
{100107,"Harry Potter and the Deathly Hallows"},
{100108,"The Capture"},
{100109,"The Journey"},
{100110,"The Rescue"}};
Console.WriteLine("The Library");
PrintEnumerable(MyBooks);
// 注意 LINQ 的查询结果一般是 IEnumerable<T>。
// IEnumerable<T> 只支持一个方法，那就是 GetEnumerator 。
// 虽然理论上来讲，下面的变量定义都可以使用（而且建议使用） var ，
// 在此处为了强调期间，均使用了显式的变量类型。
// 排序。
// 注意 LINQ 的查询是延迟执行（Lazy Evaluation）的。具体情况可以参阅 MSDN。
Console.WriteLine("Ordered by Name");
PrintEnumerable(MyBooks.OrderBy(book => book.Name));
// 筛选。
IEnumerable<Book> HarryPotter = MyBooks.Where(book => book.Name.Contains("Harry Potter"));
Console.WriteLine("Harry Potter");
PrintEnumerable(HarryPotter);
// 投影。
IEnumerable<String> HarryPotterAnd = HarryPotter.Select(book => book.Name.Replace("Harry Potter and the ", ""));
Console.WriteLine("Harry Potter And ...");
PrintEnumerable(HarryPotterAnd);
// 聚合。
Console.WriteLine("First Book : " + MyBooks.First());
Console.WriteLine("Last Book : " + MyBooks.Last());
Console.WriteLine("Min Id : " + MyBooks.Max(book => book.Id));
Console.WriteLine("Max Id : " + MyBooks.Max(book => book.Id));
// 此处注意，IEnumerable 没有 Count 方法，因此 Count 其实是将所有的元素遍历一遍，然后清点数量的。
// 也就是说，此操作的时间复杂度应该是 O(n)，其中 n 是 IEnumerable 中元素的数量。
Console.WriteLine("HarryPotter Books Count : " + HarryPotter.Count());
}
}
class BookCollection : List<Book>
{
public void Add(int id, string name)
{
Add(new Book(id,name));
}
}
class Book
{
public int Id { get; set; }
public string Name { get; set; }
public override string ToString()
{
return string.Format("[{0}]{1}", Id, Name);
}
public Book(int id, string name)
{
Id = id;
Name = name;
}
}
}
运行结果如下
The Library [100101]Harry Potter and the Philosopher's Stone [100102]Harry Potter and the Chamber of Secrets [100103]Harry Potter and the Prisoner of Azkaban [100104]Harry Potter and the Goblet of Fire [100105]Harry Potter and the Order of the Phoenix [100106]Harry Potter and the Half-Blood Prince [100107]Harry Potter and the Deathly Hallows [100108]The Capture [100109]The Journey [100110]The Rescue ========== Ordered by Name [100102]Harry Potter and the Chamber of Secrets [100107]Harry Potter and the Deathly Hallows [100104]Harry Potter and the Goblet of Fire [100106]Harry Potter and the Half-Blood Prince [100105]Harry Potter and the Order of the Phoenix [100101]Harry Potter and the Philosopher's Stone [100103]Harry Potter and the Prisoner of Azkaban [100108]The Capture [100109]The Journey [100110]The Rescue ========== Harry Potter [100101]Harry Potter and the Philosopher's Stone [100102]Harry Potter and the Chamber of Secrets [100103]Harry Potter and the Prisoner of Azkaban [100104]Harry Potter and the Goblet of Fire [100105]Harry Potter and the Order of the Phoenix [100106]Harry Potter and the Half-Blood Prince [100107]Harry Potter and the Deathly Hallows ========== Harry Potter And ... Philosopher's Stone Chamber of Secrets Prisoner of Azkaban Goblet of Fire Order of the Phoenix Half-Blood Prince Deathly Hallows ========== First Book : [100101]Harry Potter and the Philosopher's Stone Last Book : [100110]The Rescue Min Id : 100110 Max Id : 100110 HarryPotter Books Count : 7 请按任意键继续. . .
LINQ to XML
使用以下文档
<?xml version="1.0" encoding="utf-8" ?>
<!-- 样例 XML -->
<!-- 注意：XML中的标识符是区分大小写的。 -->
<!-- 注意：XML中的标识符一般采用首字母小写的 Camel 命名法。（如 myIdentifierType） -->
<library name="CXs' Library">
<series id="5001" name="Guardians of Ga'Hoole">
<book id="100101" name="The Capture" author="Kathryn Lasky" />
<book id="100102" name="The Journey" author="Kathryn Lasky" />
</series>
<series id="5002" name="Harry Potter">
<book id="100201" name="Harry Potter and the Philosopher's Stone" author="J. K. Rowling" />
<book id="100202" name="Harry Potter and the Chamber of Secrets" author="J. K. Rowling" />
</series>
<book id="100501" name="Introduction to Algorithms" author="Thomas H. Cormen" />
<book id="100502" name="The Art Of Computer Programming" author="Donald E. Knuth" />
</library>
使用以下代码
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Linq;
namespace ConsoleApplication1
{
class Program
{
static void PrintBook(XElement xBook)
{
Console.WriteLine("Book : [{0}] {1}, by {2}", (int)xBook.Attribute("id"),
(string)xBook.Attribute("name"), (string)xBook.Attribute("author"));
}
static void Main(string[] args)
{
var doc = XDocument.Load("XmlFile1.xml");
Console.WriteLine("Root : {0}", doc.Root.Name);
// 注意：XML名称是区分大小写的。
Console.WriteLine("Library : {0}", (string)doc.Root.Attribute("name"));
// 枚举所有的图书系列。
foreach (var s in doc.Root.Elements("series"))
{
Console.WriteLine("== Series : [{0}] {1} ==", (int)s.Attribute("id"),
(string)s.Attribute("name"));
foreach (var book in s.Elements("book")) PrintBook(book);
Console.WriteLine("=======================");
}
// 枚举所有的独立图书。
foreach (var book in doc.Root.Elements("book")) PrintBook(book);
}
}
}
运行结果如下
Root : library Library : CXs' Library == Series : [5001] Guardians of Ga'Hoole == Book : [100101] The Capture, by Kathryn Lasky Book : [100102] The Journey, by Kathryn Lasky ======================= == Series : [5002] Harry Potter == Book : [100201] Harry Potter and the Philosopher's Stone, by J. K. Rowling Book : [100202] Harry Potter and the Chamber of Secrets, by J. K. Rowling ======================= Book : [100501] Introduction to Algorithms, by Thomas H. Cormen Book : [100502] The Art Of Computer Programming, by Donald E. Knuth 请按任意键继续. . .