LINQ 函数的实战演练测试

1、首先定义一个图书类。专门存放图书的属性信息。

代码如下：

 

//Book.cs
 
using System;
 
namespace LinqTest
{
    public class Book
    {
        public string Name { get; set; }
        public string Author { get; set; }
        public decimal Price { get; set; }
        public DateTime ReleaseDate { get; set; }
 
        public Book()
        {
 
        }
 
        public Book(string name, string anthor, decimal price, DateTime releasedata)
        {
            Name = name;
            Author = anthor;
            Price = price;
            ReleaseDate = releasedata;
        }
    }
}
 

 

2、接着新建一个类专门用来对图书类进行操作。代码如下：

 

//BookManage.cs
 
using System;
using System.Collections.Generic;
 
namespace LinqTest
{
    public static class BookManage
    {
        private static List<Book> _books;
 
        public static IList<Book> GetBook()
        {
            return _books ?? (_books = new List<Book>()
                   {
                       new Book("He", "Joke", 133, new DateTime(20160101)),
                       new Book("She", "Bob", 222, new DateTime(20110603)),
                       new Book("I", "Cham", 999, new DateTime(19910602))
                   });
        }
    }
}

 

3、最后在主程序中执行。

 

//Program.cs
 
using System;
using System.Collections.Generic;
using System.Linq;
 
namespace LinqTest
{
    internal class Program
    {
        private static void Main()
        {
            Console.WriteLine("/**Select Test*/
");
            var test = BookManage.GetBook().Where(c => c.Author.StartsWith("J")).Select(c => new
            {
                c.Name,
                c.Author,
                c.Price,
                c.ReleaseDate
            });
            foreach (var i in test)
            {
                Console.WriteLine(i);
            }
 
            Console.WriteLine("
/**SelectMany Test*/");
            var list1 = new List<int>() { 1, 2, 3, 4, 5, 6 };
            var list2 = new List<int>() { 3, 2, 3, 1 };
 
            var query = list1.SelectMany(c => list2);
            foreach (var variable in query)
            {
                Console.Write("{0}", variable);
            }
            Console.WriteLine("
");
 
            Console.WriteLine("
/*GroupBy test**/
");
            var list3 = new List<int>() { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
 
            var group = list3.GroupBy(c => c);
 
            foreach (var variable in group)
            {
                Console.WriteLine("{0} Count : {1}", variable.Key, variable.Count());
            }
            Console.WriteLine("
/*ToLookUp**/
");
            var list4 = new List<Book>()
            {
                new Book("A","B",11,new DateTime(123146)),
                new Book("AA","BB",222,new DateTime(4567895)),
                new Book("AAA","BBB",333,new DateTime(4564654)),
                new Book("A","BBB",444,new DateTime(7898465))
            };
 
            var lookup = list4.ToLookup(c => c.Name);
 
            foreach (var v in lookup)
            {
                Console.WriteLine("=====Group : {0}====", v.Key);
                foreach (var g in v)
                {
                    Console.WriteLine("Author: {0} ,Price: {1}, Release: {2}", g.Author, g.Price, g.ReleaseDate);
                }
            }
 
            Console.WriteLine("
OderBy  And Thenby Test!
");
            var orderquery = list4.OrderBy(c => c.Price).ThenBy(c => c.Name).Select(c => new
            {
                c.Name,
                c.Author,
                c.Price,
                c.ReleaseDate
            });
            foreach (var item in orderquery)
            {
                Console.WriteLine(item);
            }
 
            Console.WriteLine("
获取集合测试！
");
            var list5 = new List<int>() { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
 
            var newList = list5.Where(c => c > 3).ToList().Select(c => new
            {
                c
            });
 
            foreach (var r in newList)
            {
                Console.WriteLine(r);
            }
 
            Console.WriteLine(" 
聚合和汇总测试
");
            const double myBalance = 100.0;
            int[] withdramItem = { 20, 30, 40, 50, 60, 70, 80 };
            var banlance = withdramItem.Aggregate(myBalance, (originbalance, nextwithdraw) =>
            {
                Console.WriteLine("originbalance:{0},nextwithdraw {1}", originbalance, nextwithdraw);
                Console.WriteLine("Withdraw status:{0}", (nextwithdraw <= originbalance) ? "OK" : "Failed");
                return ((nextwithdraw <= originbalance) ? (originbalance - nextwithdraw) : originbalance);
            });
            Console.WriteLine("Ending Balance:{0}", banlance);
 
            Console.WriteLine("
***筛选***
");
 
            var query1 = BookManage.GetBook().Where(c => c.Price > 1).Select(c => new
                {
                    c.Name,
                    c.Author,
                    c.Price,
                    c.ReleaseDate
                }).Take(2);
            foreach (var r in query1)
            {
                Console.WriteLine("{0}", r);
            }
        }
    }
}

 

4、运行结果如下：