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.NET: Where and OrderBy - Language Integrated Query (LINQ)
Language Integrated Query (LINQ) Tutorial - Page 1.
Introduction
Language Integrated Query, or LINQ, integrates query syntax inside the C# language. Accessing different sources is possible using the same syntax.
Some examples using arrays as the data source:
using System;
using System.Linq;
class LinqExample
{
static void Main()
{
string[] products = { "kiwi", "almond", "banana", "apple", "grapefruit", "orange", "cucumber", "papaya", "apricot", "grapes" };
var prodQuery = from p in products
where p.StartsWith("a")
orderby p ascending
select p;
Console.WriteLine("\r\nPRODUCTS:");
foreach (string s in prodQuery)
{
Console.WriteLine(s);
}
}
}
PRODUCTS: almond apple apricot
Using Lambda with the Methods Where() and OrderBy()
This is another way to write the same thing using LINQ methods.
using System;
using System.Linq;
class LinqExample
{
static void Main()
{
string[] products = { "kiwi", "almond", "banana", "apple", "grapefruit", "orange", "cucumber", "papaya", "apricot", "grapes" };
var prodQuery = products.Where(p => p.StartsWith("a")).OrderBy(p => p);
Console.WriteLine("\r\nPRODUCTS:");
foreach (string s in prodQuery)
{
Console.WriteLine(s);
}
}
}
An example with numbers:
using System;
using System.Linq;
class LinqExample
{
static void Main()
{
int[] nums = { 9, 2, 3, 7, 1, 0, 8, 5, 4, 6 };
var numQuery = from n in nums
where n >= 3 && n <= 7
orderby n ascending
select n;
Console.WriteLine("\r\nNUMBERS:");
foreach (int i in numQuery)
{
Console.WriteLine(i.ToString());
}
}
}
NUMBERS: 3 4 5 6 7
Now the same with LINQ methods:
using System;
using System.Linq;
class LinqExample
{
static void Main()
{
int[] nums = { 9, 2, 3, 7, 1, 0, 8, 5, 4, 6 };
var numQuery = nums.Where(n => n >= 3 && n <= 7).OrderBy(n => n);
Console.WriteLine("\r\nNUMBERS:");
foreach (int i in numQuery)
{
Console.WriteLine(i.ToString());
}
}
}
The below statement is a LINQ query. The clauses from
, where
, orderby
, ascending
,
descending
, and select
are keywords.
var numQuery = from n in nums where n >= 3 && n <= 7 orderby n ascending select n;
A LINQ example using a List
:
using System;
using System.Collections.Generic;
using System.Linq;
class LinqExample
{
static void Main()
{
List<string> names = new List<string> { "Xavier", "John", "David", "Jack", "Aaron" };
var namQuery = from n in names
where n.StartsWith("J")
orderby n ascending
select n;
Console.WriteLine("\r\nNAMES: (first iteration)");
foreach (string s in namQuery)
{
Console.WriteLine(s);
}
names.Add("Jill");
names.Add("Edward");
Console.WriteLine("\r\nNAMES: (second iteration)");
foreach (string s in namQuery)
{
Console.WriteLine(s);
}
}
}
NAMES: (first iteration) Jack John NAMES: (second iteration) Jack Jill John
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