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Querying With LINQ

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Some Final Advice

3:15 with Carling Kirk

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 and foreach 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 0:00
    query all the things. 0:04
    What we've been using in this course is referred to as LINQ to Objects 0:07
    which means that we've been using LINQ on in-memory collections. 0:11
    But you can also use LINQ with remote data sources, or 0:15
    data that doesn't exist within your program, by the use of LINQ providers. 0:19
    When you see the phrase LINQ to, it usually means that it's a LINQ provider. 0:24
    A LINQ provider is a piece of software that enables 0:29
    the use of LINQ to query an external datasource. 0:32
    Some popular providers are LINQ to SQL, LINQ to XML, 0:36
    and there's even a LINQ to Twitter. 0:40
    LINQ to Entities is a provider that's used with Entity Framework, 0:42
    which you'll learn about here at Treehouse too. 0:46
    I've put a list of some common providers in the teacher's notes for 0:49
    you to check out. 0:52
    These providers implement an interface that we haven't covered here called 0:54
    IQueryable. 0:58
    IQueryable inherits from IEnumerable, and it lets us use all the LINQ 0:59
    methods that we've covered in this course You can usually use Iquerable is 1:04
    just as you would with IEnumerable but there's one thing to keep in mind. 1:08
    Remember when we talked about deferred execution with, 1:13
    LINQ providers you're working with the remote data source. 1:16
    So it's important to keep in mind when your query actually executes. 1:20
    You can build a giant query with multiple WHERE clauses and joins and sorting but 1:24
    nothing actually happens until you iterate over the result. 1:29
    Sometimes you'll write a query and it will be super slow as you get more familiar 1:34
    with LINQ there are some strategies that you can use to make your queries faster. 1:39
    Certain LINQ operators execute immediately aggregate operators like sum and 1:44
    count have to iterate over everything in the collection in order to evaluate. 1:49
    Is your query executing before it has to? 1:54
    Does it fetch data from the remote source multiple times? 1:57
    How many times does it iterate over a collection, and over how many elements? 2:01
    If you search Stack Overflow for the terms slow LINQ query. 2:05
    You'll see a ton of people asking for advice on their queries. 2:10
    Don't hesitate to ask for help. 2:14
    Sometimes the answer stares you right in the face, but 2:16
    it takes another set of eyes to actually see it. 2:18
    The Treehouse community is a great place to ask for 2:20
    help another thing I like to do is break the query apart and 2:24
    time it like we did with comparing union and can cat operators. 2:28
    Also keep in mind how much data you're returning. 2:32
    Make use of projection with the select operator 2:36
    to create anonymously typed objects that contain only what you need. 2:38
    I love LINQ because it lets me do so much with fewer lines of code. 2:44
    The next time you start to write a for 2:49
    each loop, think to yourself, can I use LINQ for this? 2:50
    The more you practice writing LINQ queries, the more natural it will feel. 2:54
    Do you already have some projects where you can practice using LINQ? 3:00
    If not check the teachers notes for 3:03
    some ideas, we'll be using LINQ often in the courses that follow. 3:05
    Especially when we get into using databases in our applications 3:09
    are you excited. 3:12
    I know I am. 3:13

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