static void TestQuerySyntax()
{
List <int> numbers = new List <int> {
2, 4, 8, 16, 32
};
IEnumerable <int> evenNumbers = (from number in numbers
where number > 10
select number);
// collection of objects
var birds = new SimpleBirdRepository().GetBirds();
// query projection - use anonymous type for the result
var redBirdds = from b in birds
where b.Color.Equals("Red", StringComparison.OrdinalIgnoreCase) && b.Sightings > 2
select new { BirdName = b.Name, b.Sightings };
// create object of anonymous type; IMPORTANT: properties are R/O!
var anonymousPidgeon = new { Name = "Pidgeon", Color = "White", Sightings = 10 };
var canary = new SimpleBird {
Name = "Canary", Color = "Yellow", Sightings = 0
};
birds.Add(canary);
var matchingBirds = from b in birds
where b.Color != anonymousPidgeon.Color
orderby b.Name descending, b.Color
select new { BirdName = b.Name };
// grouping; use "into" to include grouping result in a "where" clause
var birdCol = from b in birds
group b by b.Color
into birdsByColor
where birdsByColor.Count() > 1
select new { Color = birdsByColor.Key, Count = birdsByColor.Count() };
}
static void TestMethodSyntax()
{
var birds = new SimpleBirdRepository().GetBirds();
// use method syntax instead of query syntax
var redBirds = birds
.Where(b => b.Color.Equals("red", StringComparison.OrdinalIgnoreCase))
.OrderBy(b => b.Name)
.ThenByDescending(b => b.Sightings)
.Select(b => new { BirdName = b.Name, b.Sightings });
// quantifiers: Any(), All()
// take elements: First[OrDefault](), Single[OrDefault](), Last[OrDefault](), ElementAt[OrDefault]()
// partitioning operators: Skip(), Take(), SkipWhile(), TakeWhile()
var birdsWithLongName = birds
.OrderBy(b => b.Name.Length)
.SkipWhile(b => b.Name.Length < 6);
// join operators: Join(), GroupJoin()
var colors = new List <string> {
"Red", "White", "Purple"
};
// use query syntax
var favColorBirds = from b in birds
join c in colors on b.Color equals c
select b;
// use method syntax
var theSameBirds = birds.Join(colors, b => b.Color, c => c, (b, c) => b);
var groupedBirds = colors.GroupJoin(
birds,
c => c,
b => b.Color,
(c, b) => new { Color = c, Birds = b });
var allGroupedBirds = groupedBirds.SelectMany(g => g.Birds);
// aggregations: Count(), Sum(), Average(), Min(), Max()
var birdCountByColor = birds
.GroupBy(b => b.Color)
.Select(g => new { Color = g.Key, Count = g.Count(), Sightings = g.Sum(b => b.Sightings) }); // note the use of property "Key" - the grouping field
// set operators: Distinct(), Except(), Union(), Intersect(), Concat()
birds.Add(new SimpleBird {
Name = "Pelican", Color = "Pink", Sightings = 6
});
var birdColors = birds.Select(b => b.Color).Distinct(); // remove duplicates
var colorWithNoBirds = colors.Except(birds.Select(b => b.Color).Distinct());
var allColors = colors.Union(birds.Select(b => b.Color).Distinct());
var matchingColors = colors.Intersect(birds.Select(b => b.Color).Distinct());
var combinedColors = colors.Concat(birds.Select(b => b.Color).Distinct()); // does not remove duplicates in the sets
// generation operators: Range(), Repeat(), Empty(), DefaultIfEmpty()
var numbers = Enumerable.Range(0, 10);
var blankBirds = Enumerable.Repeat(new SimpleBird(), 5);
var emptyBirds = Enumerable.Empty <SimpleBird>();
var emptyBird = emptyBirds.DefaultIfEmpty(); // returns null
// conversion operators: ToList(), ToArray(), AsEnumerable(), ToDictionary(), ...
}
