This article shows how to select exact match and in between
items from a collection using LINQ and C#. Now open Visual Studio 2010 click on
New Project in the File menu of Visual Studio 2010, select C# with console
application from the selected templates.
Note
If you want to write your sample code in VB.NET, Select other Language
-> Visual Basic with console application in
the Project types in the Templates pane.
See Figure 1.
Figure 1.
As name suggests, LINQ (.NET Integrated Query Language)
provides from..where..select syntax to select
data
from collections.
Understanding from..where..select
The from..where..select syntax in LINQ is similar to
SELECT..FROM..WHERE clause of SQL. Here is a simple from..select.
from
day in daysArray
select day;
In the above statement, I select day in
daysArray. It returns an object of "var" type, which is a generic type and can
store any type. For example, daysArray can be an array of numbers, strings, or
even objects. Here is an example of daysArray.
string[]
daysArray = { "Mon",
"Tue",
"Wed", "Thur",
"Fri",
"Sat", "Sun" };
This is how return value is stored from a
from..select statement.
var
days = from day
in daysArray
select day;
Now where clause is used to filter the
results. For example, the following syntax gets retuslts from daysArray where
value of day is "Wed" only.
var
days = from day
in daysArray
where day =="Wed"
select day;
Filtering using where
The following code selects items from an array that have
value below 20.
int[]
IntArray = { 12, 5, 24, 10, 9, 8, 4, 87, 23, 7, 11, 43 };
var under20 =
from u20 in
IntArray where u20 < 20
select u20;
Console.WriteLine("Numbers
below 20 are: ");
Console.WriteLine("=====================");
foreach (var
numU20 in under20)
{
Console.WriteLine(numU20);
}
Console.WriteLine("======================");
Console.ReadLine();
The output looks like Figure 2.
Figure 2.
The following query is used to get items between two
values, greater than 8 and less than 20.
var
under20 = from u20
in IntArray where u20 < 20 && u20 > 8
select u20;
The output looks like Figure 3.
Figure 3.
The exact match items can be retrieved using == operator.
For example, the following syntax selects items that have value 23.
var
under20 = from u20
in IntArray where u20 == 23
select u20;
The output looks like Figure 4.
Figure 4.