Linq案例

1.牛刀小试

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace linq
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] words = { "hello","linq","good","wonderful"};

            var shortWords = from word in words
                             where word.Length <= 5
                             select word;
            foreach (var word in shortWords)
            {
                Console.WriteLine(word);
            }
            Console.ReadKey();
        }
    }
}

2.Group分组处理

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace linq
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] words = { "hello","linq","good","wonderful","world","beautiful"};
            //VAR 是3.5新出的一个定义变量的类型，其实也就是弱化类型的定义。VAR可代替任何类型，编译器会根据上下文来判断你到底是想用什么类型的。
            var groups = from word in words
                         orderby word ascending
                         group word by word.Length into lengthGroups
                         orderby lengthGroups.Key descending
                         select new { Length = lengthGroups.Key, Words = lengthGroups }; // 按长度将单词分组

            foreach (var group in groups)
            {
                Console.WriteLine("Words of length" + group.Length);
                foreach (string word in group.Words)
                {
                    Console.WriteLine(" " + word);
                }
            }
            Console.ReadKey();
        }
    }
}

3.XML 案例

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Linq;
using System.Threading.Tasks;

namespace linq
{
    class Book
    {
        public string Publisher;
        public string Title;
        public int Year;

        public Book(string title,string publisher,int year)
        {
            Title = title;
            Publisher = publisher;
            Year = year;
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            Book[] books = new Book[]
            {
                new Book("Ajax","Zhang",2015),
                new Book("Java","Li",2016),
                new Book(".Net","Zhao",2016),
            };

            XElement xml = new XElement("books",
                from book in books
                where book.Year == 2016
                select new XElement("book",
                    new XAttribute("title",book.Title),
                    new XElement("publisher",book.Publisher)
                    )
            );

            Console.WriteLine(xml);
            Console.ReadKey();
        }
    }
}