走进Linq-Linq大观园

//这样的一个集合，存储在内存中
IList<Book> books = new List<Book> {
    new Book { Title = "Inside COM", ISBN = "123-456-789",Price=20 },
    new Book { Title = "Inside C#", ISBN = "123-356-d89",Price=100 },
    new Book { Title = "Linq", ISBN = "123-d56-d89", Price = 120 }
};

数据查询阶段

var result = from book in books
            where book.Price > 50
            orderby book.Price
            select new { Key = book.Title, Value = book.Price };
foreach (var item in result)
                Console.WriteLine("Key:{0}-Value:{1}",item.Key,item.Value.ToString());

Linq to SQL(集合存储在Sql Server)

数据准备阶段,建立数据库表

输入数据

改写一下Book类，这个类是一个映射类，和数据库表做映射，更多内容后面会详细讲解

[Table]
public class Book
{
    ///
    /// 图书名称
     ///
    [Column]
    public string Title { get; set; }
    ///
    /// 单价
     ///
    [Column(DbType = "numeric(5, 2)")]
    public float Price { get; set; }
    ///
    /// 作者
     ///
    [Column]
    public string Author { get; set; }
    ///
    /// ISBN号
     ///
    [Column]
    public string ISBN { get; set; }
}

数据查询阶段

DataContext db = new DataContext("Data Source=localhost;Initial Catalog=db;User ID=sa;Password=sa");
            var result = from book in db.GetTable<Book>()
                         where book.Price > 50
                         orderby book.Price
                         select new { Key = book.Title, Value = book.Price };

            foreach (var item in result)
                Console.WriteLine("Key:{0}-Value:{1}",item.Key,item.Value.ToString());

最后程序运行的结果都是：