Linq101-Grouping Operators

 using System;
 using System.Collections.Generic;
 using System.Linq;

 namespace Linq101
 {
     class Grouping
     {
         /// <summary>
         /// This sample uses group by to partition a list of numbers by their remainder when divided by 5.
         /// </summary>
         public void Linq40()
         {
             int[] numbers = { , , , , , , , , ,  };

             var numberGroups = from n in numbers
                                group n by n %  into g
                                select new { Remainder = g.Key, Numbers = g };

             foreach (var numberGroup in numberGroups)
             {
                 Console.WriteLine("除以5余数为{0}的有：", numberGroup.Remainder);
                 foreach (var n in numberGroup.Numbers)
                 {
                     Console.WriteLine(n);
                 }
             }
         }

         /// <summary>
         /// This sample uses group by to partition a list of words by their first letter.
         /// </summary>
         public void Linq41()
         {
             string[] words = { "blueberry", "chimpanzee", "abacus", "banana", "apple", "cheese" };

             var wordGroups = from w in words
                              group w by w[] into g
                              select new { FirstLetter = g.Key, words = g };

             foreach (var wordGroup in wordGroups)
             {
                 Console.WriteLine("以字母{0}开头的单词有：", wordGroup.FirstLetter);
                 foreach (var word in wordGroup.words)
                 {
                     Console.WriteLine(word);
                 }
             }
         }

         /// <summary>
         /// This sample uses group by to partition a list of products by category.
         /// </summary>
         public void Linq42()
         {
             var products = Data.GetProductList();

             var productGroups = from p in products
                                 group p by p.Category into g
                                 select new { Category = g.Key, products = g };

             //ObjectDumper.Write(productGroups,1);

             foreach (var productGroup in productGroups)
             {
                 Console.WriteLine("分类为{0}的产品有：", productGroup.Category);
                 foreach (var product in productGroup.products)
                 {
                     ObjectDumper.Write(product);
                 }
             }
         }

         /// <summary>
         /// This sample uses group by to partition a list of each customer's orders, first by year, and then by month.
         /// </summary>
         public void Linq43()
         {
             var customers = Data.GetCustomerList();

             var customerOrderGroups = from c in customers
                                       select new
                                       {
                                           c.CompanyName,
                                           YearGroups = from o in c.Orders
                                                        group o by o.OrderDate.Year into yg
                                                        select new
                                                        {
                                                            Year = yg.Key,
                                                            MonthGoups = from o in yg
                                                                         group o by o.OrderDate.Month into mg
                                                                         select new { Month = mg.Key, mg }
                                                        }
                                       };

             ObjectDumper.Write(customerOrderGroups, );
         }

         /// <summary>
         /// This sample uses GroupBy to partition trimmed elements of an array using a custom comparer that matches words that are anagrams of each other.
         /// </summary>
         public void Linq44()
         {
             string[] anagrams = { "from   ", " salt", " earn ", "  last   ", " near ", " form  " };

             var query = anagrams.GroupBy(w => w.Trim(), new AnagramEqualityComparer());

             ObjectDumper.Write(query, );
         }

         private class AnagramEqualityComparer : IEqualityComparer<string>
         {
             public bool Equals(string x, string y)
             {
                 return getCanonicalString(x) == getCanonicalString(y);
             }

             public int GetHashCode(string obj)
             {
                 return getCanonicalString(obj).GetHashCode();
             }

             private string getCanonicalString(string word)
             {
                 char[] wordChars = word.ToCharArray();
                 Array.Sort(wordChars);
                 return new string(wordChars);
             }
         }

         /// <summary>
         /// 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.
         /// </summary>
         public void Linq45()
         {
             string[] anagrams = { "from   ", " salt", " earn ", "  last   ", " near ", " form  " };

             var query = anagrams.GroupBy(w => w.Trim(),
                 a => a.ToUpper(),
                 new AnagramEqualityComparer());

             ObjectDumper.Write(query, );
         }
     }
 }