1 using System;  2 using System.Collections.Generic;  3 using System.Linq;  4   5 namespace Linq101  6 {  7     class Grouping  8     {  9         /// <summary> 10         /// This sample uses group by to partition a list of numbers by their remainder when divided by 5. 11         /// </summary> 12         public void Linq40() 13         { 14             int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; 15  16             var numberGroups = from n in numbers 17                                group n by n % 5 into g 18                                select new { Remainder = g.Key, Numbers = g }; 19  20             foreach (var numberGroup in numberGroups) 21             { 22                 Console.WriteLine("除以5余数为{0}的有：", numberGroup.Remainder); 23                 foreach (var n in numberGroup.Numbers) 24                 { 25                     Console.WriteLine(n); 26                 } 27             } 28         } 29  30         /// <summary> 31         /// This sample uses group by to partition a list of words by their first letter. 32         /// </summary> 33         public void Linq41() 34         { 35             string[] words = { "blueberry", "chimpanzee", "abacus", "banana", "apple", "cheese" }; 36  37             var wordGroups = from w in words 38                              group w by w[0] into g 39                              select new { FirstLetter = g.Key, words = g }; 40  41             foreach (var wordGroup in wordGroups) 42             { 43                 Console.WriteLine("以字母{0}开头的单词有：", wordGroup.FirstLetter); 44                 foreach (var word in wordGroup.words) 45                 { 46                     Console.WriteLine(word); 47                 } 48             } 49         } 50  51         /// <summary> 52         /// This sample uses group by to partition a list of products by category. 53         /// </summary> 54         public void Linq42() 55         { 56             var products = Data.GetProductList(); 57  58             var productGroups = from p in products 59                                 group p by p.Category into g 60                                 select new { Category = g.Key, products = g }; 61  62             //ObjectDumper.Write(productGroups,1); 63  64             foreach (var productGroup in productGroups) 65             { 66                 Console.WriteLine("分类为{0}的产品有：", productGroup.Category); 67                 foreach (var product in productGroup.products) 68                 { 69                     ObjectDumper.Write(product); 70                 } 71             } 72         } 73  74         /// <summary> 75         /// This sample uses group by to partition a list of each customer‘s orders, first by year, and then by month. 76         /// </summary> 77         public void Linq43() 78         { 79             var customers = Data.GetCustomerList(); 80  81             var customerOrderGroups = from c in customers 82                                       select new 83                                       { 84                                           c.CompanyName, 85                                           YearGroups = from o in c.Orders 86                                                        group o by o.OrderDate.Year into yg 87                                                        select new 88                                                        { 89                                                            Year = yg.Key, 90                                                            MonthGoups = from o in yg 91                                                                         group o by o.OrderDate.Month into mg 92                                                                         select new { Month = mg.Key, mg } 93                                                        } 94                                       }; 95  96             ObjectDumper.Write(customerOrderGroups, 3); 97         } 98  99         /// <summary>100         /// This sample uses GroupBy to partition trimmed elements of an array using a custom comparer that matches words that are anagrams of each other.101         /// </summary>102         public void Linq44()103         {104             string[] anagrams = { "from   ", " salt", " earn ", "  last   ", " near ", " form  " };105 106             var query = anagrams.GroupBy(w => w.Trim(), new AnagramEqualityComparer());107 108             ObjectDumper.Write(query, 1);109         }110 111         private class AnagramEqualityComparer : IEqualityComparer<string>112         {113             public bool Equals(string x, string y)114             {115                 return getCanonicalString(x) == getCanonicalString(y);116             }117 118             public int GetHashCode(string obj)119             {120                 return getCanonicalString(obj).GetHashCode();121             }122 123             private string getCanonicalString(string word)124             {125                 char[] wordChars = word.ToCharArray();126                 Array.Sort(wordChars);127                 return new string(wordChars);128             }129         }130 131         /// <summary>132         /// This sample uses GroupBy to partition trimmed elements of an array using a custom comparer that matches words that are anagrams of each other, and then converts the results to uppercase.133         /// </summary>134         public void Linq45()135         {136             string[] anagrams = { "from   ", " salt", " earn ", "  last   ", " near ", " form  " };137 138             var query = anagrams.GroupBy(w => w.Trim(),139                 a => a.ToUpper(),140                 new AnagramEqualityComparer());141 142             ObjectDumper.Write(query, 1);143         }144     }145 }