- All About LINQ 3:20
- All About LINQ 2 questions
- Writing Your First LINQ Query 8:12
- Using Query Syntax 2 objectives
- Object Initialization 4:14
- Object Initialization 1 objective
- Selecting, Projecting and Anonymous Types 8:24
- Selecting, Projecting and Anonymous Types 2 objectives
- Ordering and Grouping 6:04
- Ordering and Grouping 5 questions
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All About LINQ
3:20What is LINQ and how can we use it?
Hi I'm Carling,
I'm a Treehouse teacher and a developer.
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In this course,
I'm going to teach you all about LINQ.
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LINQ is a powerful toolset
in the .NET Framework
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that enables C# developers to query and
manipulate collections of objects.
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LINQ stands for language integrated query.
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LINQ was introduced in C# 3.0 to give
developers the querying power of
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a database querying language like SQL.
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If you've used SQL, or S-Q-L,
LINQ will seem pretty familiar.
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But if you haven't, no worries.
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You can still learn to use
LINQ with this course.
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LINQ doesn't really provide
much we couldn't do before, so
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then why would we use it?
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Why reinvent the wheel?
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Well, it makes it way easier and
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faster to write code that would otherwise
be verbose and complicated to read.
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Before LINQ if we wanted to get
a subset of objects from a collection,
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we would write a loop, compare each object
to see if it was the one we want and
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then stick it into a new collection.
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It could end up being 20 lines long.
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Now with LINQ,
we can do it with only one line of code.
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And even better,
our code becomes more readable and
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self-documenting because
the methods we'll use like Where or
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OrderBy are more like writing
a sentence than actual code.
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Along with LINQ came a lot of other new
language features to help support it.
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We'll touch on all these along the way
as we learn to query with LINQ, but
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you can find a list of them
in the teacher's notes.
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So how do we use LINQ?
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We can use LINQ on collections
like arrays or lists.
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If you haven't heard of a list or
a collection yet, you should check out
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the teacher's notes for
more resources before diving into LINQ.
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But more specifically we can use
LINQ with anything that implements
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IEnumerable of T in
the system.collections.genericnamespace.
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IEnumerable is an interface in the .NET
framework that, when implemented for
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a type,
tells us that it has an enumerator.
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That means that the objects in it can be
looped through like we do in a for or
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a for each loop.
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If all this sounds unfamiliar to you,
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you should check out our course on C#
objects to learn about arrays and loops.
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You can find a link in
the teacher's notes.
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I'll be using the terms collections and
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sequences interchangeably
throughout this course.
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Just keep in mind that if I use either
term, it's really anything that implements
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IEnumerable or, more generally,
anything that we can use LINQ with.
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There are two flavors of syntax we
can use when writing LINQ queries,
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query syntax and method syntax.
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Every developer has their preference,
but there are some
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things you can do with method syntax
that you can't do with query syntax.
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We're going to start out by using query
syntax, but since you'll probably be
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reading both in the future, we'll get
into using method syntax a little later.
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Using method syntax requires getting into
those supporting language features I
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mentioned earlier.
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All right, my fingers are itching to code.
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Let's open up Workspaces and
start playing with LINQ.
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