Slide 1
Slide 1 text
LINQ: A simple Introduction
Fanie Reynders
Technical Team Lead
@FanieReynders
Slide 2
Slide 2 text
Agenda
What is LINQ?
LINQ Queries
Examples
Exploring a LINQ to * scenario
Slide 3
Slide 3 text
What is LINQ?
LINQ (pronounced "link")
-
Language Integrated Query
Microsoft .NET Framework component
Extends powerful query capabilities to the language
syntax in .NET
Introduces standard, easily-learned patterns for querying
and updating data
Extendable
Slide 4
Slide 4 text
LINQ Queries: Overview
3 parts of a LINQ Query:
// 1. Data source.
int[] numbers = new int[7] { 0, 1, 2, 3, 4, 5, 6 };
// 2. Query creation.
// numQuery is an IEnumerable
var numQuery = from num in numbers
where (num % 2) == 0
select num;
// 3. Query execution.
foreach (int num in numQuery) {
Console.Write("{0,1} ", num);
}
Slide 5
Slide 5 text
LINQ Queries: Query operation
Data source
Query
from...
where...
select...
Execution
foreach (int item in )
Query
Return each item
item
Do something with item
…
Get next item
Slide 6
Slide 6 text
LINQ Queries: Data sources
In memory
o IEnumerable
o IList
o Array (or [])
o ICollection
Derived on-demand
o IQueryable
Slide 7
Slide 7 text
LINQ Queries: Query structure
From
Join
Group
Where
OrderBy
Select
Slide 8
Slide 8 text
LINQ Queries: Comparison with SQL
SELECT
*
FROM
People AS p
WHERE
p.City = 'Johannesburg'
ORDER BY
p.Surname
from p in People
where p.City == "Johannesburg"
orderby p.Surname
select p;
LINQ Query: SQL Query:
Slide 9
Slide 9 text
LINQ Queries: Using Lambdas
var joburgPeople = from p in People
where p.City == "Johannesburg"
orderby p.Surname
select p;
Using Lamda Expressions:
var joburgPeople = People.Where(p => p.City == "Johannesburg")
.OrderBy(p => p.Surname)
.Select(p => p);
Slide 10
Slide 10 text
Demo Time!
#hopeitworks
Slide 11
Slide 11 text
LINQ to *
Amazon
Active Directory
CSV
Datasets
Entities
Excel
Facebook
Files
Google
Oracle
RegEx
SQL
Twitter
XML
etc…
Slide 12
Slide 12 text
LINQ to *: Case study
For the stock code “MSFT” we need to search Facebook
for the people who likes it as well as Twitter for the
followers of Microsoft, then combine it with all our
customers under the age of 55 that lives in any of our
operational areas including the latest price from NASDAQ.
This information need to be merged, ordered by surname
and grouped by age. We need to export it to an Excel
Spreadsheet.
Slide 13
Slide 13 text
LINQ to *: Possibilities
Facebook Twitter NASDAQ
SQL XML Excel
1
1
1
3
2
Slide 14
Slide 14 text
Demo Time!
Thank you