phattrienweb

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
 
var orderedNumbers = from n in numbers
                     orderby n % 2 == 0 descending
                     select n;
 
foreach (var g in orderedNumbers)
{
    Console.Write("{0},", g);
} 

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
 
var numberGroups = from n in numbers
                   group n by n % 2 into g
                   select new { Remainder = g.Key, Numbers = g };
 
foreach (var g in numberGroups)
{
    if(g.Remainder.Equals(0))
        Console.WriteLine("Even Numbers:", g.Remainder);
    else
        Console.WriteLine("Odd Numbers:", g.Remainder);
    foreach (var n in g.Numbers)
    {
        Console.WriteLine(n);
    }
}

Odd Numbers:
5
1
3
9
7
Even Numbers:
4
8
6
2
0

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.ToString().ToLower(), Words = g };
 
foreach (var g in wordGroups)
{
    Console.WriteLine("Words that start with the letter '{0}':", g.FirstLetter);
    foreach (var w in g.Words)
    {
        Console.WriteLine(w);
    }
}

Words that start with the letter 'b':
blueberry
Words that start with the letter 'c':
Chimpanzee
Words that start with the letter 'a':
abacus
apple
Words that start with the letter 'b':
Banana
Words that start with the letter 'c':
cheese

string[] words = { "blueberry", "Chimpanzee", "abacus", "Banana", "apple", "cheese" };
 
var wordGroups = from w in words
                 group w by w[0].ToString().ToLower() into g
                 select new { FirstLetter = g.Key.ToString().ToLower(), Words = g };
 
foreach (var g in wordGroups)
{
    Console.WriteLine("Words that start with the letter '{0}':", g.FirstLetter);
    foreach (var w in g.Words)
    {
        Console.WriteLine(w);
    }
}

Words that start with the letter 'b':
blueberry
Banana
Words that start with the letter 'c':
Chimpanzee
cheese
Words that start with the letter 'a':
abacus
apple

var wordGroups = from w in words
orderby w[0].ToString().ToLower()
group w by w[0].ToString().ToLower() into g
select new { FirstLetter = g.Key.ToString().ToLower(), Words = g };

public class Customer
{
    public List<Order> Orders { get; set; }
}
 
public class Order
{
    public DateTime Date { get; set; }
    public int Total { get; set; }
}

List<Customer> customers = 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,
                                                         MonthGroups = from o in yg
                                                         group o by o.OrderDate.Month into mg
                                                         select new { Month = mg.Key, Orders = mg }
                                                    }
                                  };

Whew! that took a lot to copy and paste from MSDN’s sample library! 
As mentioned previously the important part here is that the keys for these are the first value after the “by”. This just creates a bunch of dictionarys keyed embeded together keyed on the values after the “by”.

public class AnagramEqualityComparer : IEqualityComparer
{
    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);
    }
}

string[] anagrams = { "from", "salt", "earn", "last", "near", "form" };
 
var orderGroups = anagrams.GroupBy(
                      w => w.Trim(),
                      a => a.ToUpper(),
                      new AnagramEqualityComparer()
                  );
 
foreach (var group in orderGroups)
{
    Console.WriteLine("For the word "{0}" we found matches to:", group.Key);
    foreach (var word in group)
    {
        Console.WriteLine(word);
    }
}