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", , new DateTime()),
                        new Book("She", "Bob", , new DateTime()),
                        new Book("I", "Cham", , new DateTime())
                    });
         }
     }
 }

 

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*/\n");
             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("\n/**SelectMany Test*/");
             var list1 = new List<int>() { , , , , ,  };
             var list2 = new List<int>() { , , ,  };

             var query = list1.SelectMany(c => list2);
             foreach (var variable in query)
             {
                 Console.Write("{0}", variable);
             }
             Console.WriteLine("\n");

             Console.WriteLine("\n/*GroupBy test**/\n");
             var list3 = new List<int>() { , , , , , , , ,  };

             var group = list3.GroupBy(c => c);

             foreach (var variable in group)
             {
                 Console.WriteLine("{0} Count : {1}", variable.Key, variable.Count());
             }
             Console.WriteLine("\n/*ToLookUp**/\n");
             var list4 = new List<Book>()
             {
                 new Book("A","B",,new DateTime()),
                 new Book("AA","BB",,new DateTime()),
                 new Book("AAA","BBB",,new DateTime()),
                 new Book("A","BBB",,new DateTime())
             };

             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("\nOderBy  And Thenby Test!\n");
             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("\n获取集合测试！\n");
             var list5 = new List<int>() { , , , , , , , ,  };

             var newList = list5.Where(c => c > ).ToList().Select(c => new
             {
                 c
             });

             foreach (var r in newList)
             {
                 Console.WriteLine(r);
             }

             Console.WriteLine(" \n聚合和汇总测试\n");
             const double myBalance = 100.0;
             int[] withdramItem = { , , , , , ,  };
             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("\n***筛选***\n");

             var query1 = BookManage.GetBook().Where(c => c.Price > ).Select(c => new
                 {
                     c.Name,
                     c.Author,
                     c.Price,
                     c.ReleaseDate
                 }).Take();
             foreach (var r in query1)
             {
                 Console.WriteLine("{0}", r);
             }
         }
     }
 }

 

4、运行结果如下：