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 = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

            var numberGroups = from n in numbers
                               group n by n % 5 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[0] 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, 3);
        }

        /// <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, 1);
        }

        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, 1);
        }
    }
}