This examples shows how to use LINQ in your programs, covering the entire range of LINQ functionality.

Example 1: This example finds all elements of an array less than 7.

           int[] allNumbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

            var lowNums1 =
                    from n in allNumbers
                    where n < 7
                    select n;

            //Version 1
            Console.WriteLine("Numbers < 7:");
            foreach (var x in lowNums1)
                Console.WriteLine(x);

            //Version 2
            var lowNums2 = allNumbers.Where(n => n < 7);
            Console.WriteLine("Numbers < 7:");
            foreach (var x in lowNums2)
                Console.WriteLine(x);

            //Both of them writes to the console window like below.
            //
            //Numbers < 7:
            //5
            //4
            //1
            //3
            //6
            //2
            //0

Example2: This example shows the partition a list of words by their first letter with "group by".

            string[] words = { "banana", "apple", "strawberry", "cheese", "pineapple", "book", "angel", "section" };
            var wordGroups1 =
                from w in words
                group w by w[0] into g
                select new { FirstLetter = g.Key, Words = g };

            //Version 1
            foreach (var g in wordGroups1)
            {
                Console.WriteLine("Words that start with the letter '{0}':", g.FirstLetter);
                foreach (var w in g.Words)
                    Console.WriteLine(w);
            }

            var wordGroups2 = words.GroupBy(w => w[0], (key, g) => new { FirstLetter = key, Words = g });
            //Version 2
            foreach (var g in wordGroups2)
            {
                Console.WriteLine("Words that start with the letter '{0}':", g.FirstLetter);
                foreach (var w in g.Words)
                    Console.WriteLine(w);
            }

            //Both of them writes to the console window like below.
            //
            //Words that start with the letter 'b':
            //banana
            //book
            //Words that start with the letter 'a':
            //apple
            //angel
            //Words that start with the letter 's':
            //strawberry
            //section
            //Words that start with the letter 'c':
            //cheese
            //Words that start with the letter 'p':
            //pineapple           

Example3: This example uses orderby to sort a list of words by length.

            string[] words = { "banana", "apple", "strawberry", "cheese", "pineapple", "book", "angel", "section" };
            var sortedWords1 =
                    from w in words
                    orderby w.Length
                    select w;

            var sortedWords2 = words.OrderBy(w => w.Length);

            //Version 1
            Console.WriteLine("The sorted list of words by length:");
            foreach (var w in sortedWords1)
                Console.WriteLine(w);

            //Version 2
            Console.WriteLine("The sorted list of words by length:");
            foreach (var w in sortedWords2)
                Console.WriteLine(w); 
            
            //Both of them writes to the console window like below.
            //
            //book
            //apple
            //angel
            //banana
            //cheese
            //section
            //pineapple
            //strawberry