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Learn about LINQ providers and get some tips on making your queries faster.
LINQ Providers
Practice Projects with LINQ
- Refactor your code: Take code you've written and change the
for
andforeach
loops into LINQ queries. - Refactor someone else's code: Find an open sourced project on Github, fork it, and see if you can refactor it with LINQ queries.
- Rock, Paper, Scissors: Create a Rock, Paper, Scissors game in a console application that keeps track of wins and losses. Report on win/lose/draw statistics after each game is played. Attempt to predict which option the player will choose to try and outsmart them!
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Now that you've got the power of LINQ in
your skill set, it's time to go out and
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query all the things.
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What we've been using in this course
is referred to as LINQ to Objects
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which means that we've been using
LINQ on in-memory collections.
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But you can also use LINQ
with remote data sources, or
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data that doesn't exist within your
program, by the use of LINQ providers.
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When you see the phrase LINQ to, it
usually means that it's a LINQ provider.
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A LINQ provider is a piece
of software that enables
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the use of LINQ to query
an external datasource.
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Some popular providers are LINQ to SQL,
LINQ to XML,
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and there's even a LINQ to Twitter.
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LINQ to Entities is a provider
that's used with Entity Framework,
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which you'll learn about
here at Treehouse too.
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I've put a list of some common
providers in the teacher's notes for
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you to check out.
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These providers implement an interface
that we haven't covered here called
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IQueryable.
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IQueryable inherits from IEnumerable,
and it lets us use all the LINQ
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methods that we've covered in this
course You can usually use Iquerable is
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just as you would with IEnumerable but
there's one thing to keep in mind.
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Remember when we talked about
deferred execution with,
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LINQ providers you're working
with the remote data source.
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So it's important to keep in mind
when your query actually executes.
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You can build a giant query with multiple
WHERE clauses and joins and sorting but
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nothing actually happens until
you iterate over the result.
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Sometimes you'll write a query and it will
be super slow as you get more familiar
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with LINQ there are some strategies that
you can use to make your queries faster.
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Certain LINQ operators execute immediately
aggregate operators like sum and
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count have to iterate over everything
in the collection in order to evaluate.
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Is your query executing before it has to?
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Does it fetch data from
the remote source multiple times?
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How many times does it iterate over
a collection, and over how many elements?
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If you search Stack Overflow for
the terms slow LINQ query.
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You'll see a ton of people asking for
advice on their queries.
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Don't hesitate to ask for help.
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Sometimes the answer stares
you right in the face, but
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it takes another set of
eyes to actually see it.
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The Treehouse community is
a great place to ask for
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help another thing I like to do
is break the query apart and
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time it like we did with comparing
union and can cat operators.
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Also keep in mind how much
data you're returning.
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Make use of projection
with the select operator
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to create anonymously typed objects
that contain only what you need.
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I love LINQ because it lets me do so
much with fewer lines of code.
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The next time you start to write a for
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each loop, think to yourself,
can I use LINQ for this?
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The more you practice writing LINQ
queries, the more natural it will feel.
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Do you already have some projects
where you can practice using LINQ?
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If not check the teachers notes for
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some ideas, we'll be using LINQ
often in the courses that follow.
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Especially when we get into using
databases in our applications
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are you excited.
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I know I am.
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