.NET – LINQ in C#

admin — Wed, 26 Mar 2008 08:51:27 +0000

LINQ (Language integrated Query)

string[] numbers = { "0042", "010", "9", "27" };
int[] nums = numbers.Select(s => Int32.Parse(s)).ToArray();
foreach (var num in nums)
Console.WriteLine(num);

What where LINQ is useful?

LINQ to Objects -

LINQ to XML -

LINQ to SQL -

LINQ to DataSet

Perform set operations on sequences of DataRow objects.
Retrieve and set DataColumn values
Obtain a LINQ standard IEnumerable sequence from a DataTable so Standard Query Operatorsmay be called.

LINQ to Entities -

101 LinQ Samples

What You can do with LINQ

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
// select var numsPlusOne =
from n in numbers
select n + 1;
// where var lowNums =
from n in numbers
where n < 5
select n;
// groupby var numberGroups =
from n in numbers
group n by n % 5 into g
select new { Remainder = g.Key, Numbers = g };
// many select
int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
int[] numbersB = { 1, 3, 5, 7, 8 };
var pairs =
from a in numbersA
from b in numbersB
where a < b
select new {a, b};
// Take – first n elements.
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var first3Numbers = numbers.Take(3);
Console.WriteLine("First 3 numbers:");
foreach (var n in first3Numbers) {
Console.WriteLine(n);
}
// Skip – This sample uses Skip to get all but the first 4 elements of the array.
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var allButFirst4Numbers = numbers.Skip(4);
var firstNumbersLessThan6 = numbers.TakeWhile(n => n > 6);
// TakeWhile (take 5, 4, 1 3)
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var firstNumbersLessThan6 = numbers.TakeWhile(n => n > 6);
// SkipWhile (allButFirst3Numbers contain 3, 9, 8, 6, 7, 8, 0)
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var allButFirst3Numbers = numbers.SkipWhile(n => n % 3 != 0);
// OrderBy
string[] words = { "cherry", "apple", "blueberry" };
var sortedWords =
from w in words
orderby w /* [ascending][descending] */
select w;
/* ascending or descending are optional, if order direction is missing
(ascending/descending) by default is sort ascending*/
// Reverse
string[] digits = { "zero", "one", "two", "three", "four",
"five", "six", "seven", "eight", "nine" };
var reversedIDigits = (
from d in digits select d)
.Reverse();
/* exemple reverse digits list*/
// DISTINCT
int[] factorsOf300 = { 2, 2, 3, 5, 5 };
var uniqueFactors = factorsOf300.Distinct();
/* uniqueFactors become something like 2, 3, 5*/
// UNION
int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
int[] numbersB = { 1, 3, 5, 7, 8 };
var uniqueNumbers = numbersA.Union(numbersB);
/* append numbersB to numbersA and store it in uniqueNumbers */
// INTERSECT
int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
int[] numbersB = { 1, 3, 5, 7, 8 };
var commonNumbers = numbersA.Intersect(numbersB);
// EXCEPT
int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
int[] numbersB = { 1, 3, 5, 7, 8 };
IEnumerable aOnlyNumbers = numbersA.Except(numbersB);
/* aOnlyNumbers contain just numbers who are in one list and not in the other */

Buy Visual studio:

Nisi's work blog » LINQ to Entities

.NET – LINQ in C#