This document discusses future directions for LINQ, including making it work with asynchronous and reactive programming using Rx. It proposes expanding LINQ to handle more types of queries, such as querying over asynchronous data streams, remote data sources, and even non-traditional domains like constraint solving. The goal is to realize a "LINQ to everything" vision by extending LINQ's principles to new programming models and domains.

2. LINQ, Take TwoRealizing the LINQ to Everything DreamBart J.F. De SmetSoftware Development EngineerMicrosoft Corporation

3. What’s LINQ?A historical perspective5 years agoLittle recent innovationWhere’s the cloud?Censored

4. Essential LINQLanguage Integrated MonadsWhy?What?How?

5. Could there be more?Essential LINQThe monadic Bind operatorIEnumerable<T>IQueryable<T>new[]{ 42 }IEnumerable<T> SelectMany<T, R>(this IEnumerable<T> source,Func<T, IEnumerable<R>> selector)SelectManyAlso see www.codeplex.com/LINQSQO for “Project MinLINQ”

6. Essential LINQMaybe monad (for fun and no profit)Null-propagating dotstring s = name?.ToUpper();One single library function sufficesSyntactic sugarname.SelectMany( _ => _.ToUpper(), s => s)from _ in namefrom s in _.ToUpper()select sCompiler

7. Essential LINQBart J.F. De SmetSoftware Development EngineerCloud Programmability Teamdemo

8. Query Providers RevisitedWhy do we have IQueryable<T>?Does it really have to be a runtime check?ImplementsIQueryable<T>varsrc = newQueryProvider<Product>();varres = from p insrcwherep.Price > 100mgroupp byp.Category;foreach(var p in res)Console.WriteLine(p);Compiles fine

9. Query Providers RevisitedLeveraging the query patternvarres = from p insrc wherep.Price > 100mgroupp byp.Category;Syntactic sugarvarres = src.Where(p => p.Price> 100m).GroupBy(p => p.Category);No GroupBy“edge”Can be instance methodsSelectWhereSource<T>Filtered<T>Projected<T>

10. Query Providers RevisitedTaking it one step furtherRecipeMethod overloadsType state machineOperator overloadsvarres = fromtweet intwitter where tweet. == “Bart”FromAboutFromLocationFrom == “LINQ” where tweet.AboutAboutAboutLocation select tweet;Query “learns”From operator overloading“Has a” typeclassTwitter{publicTwitterByFromWhere(Func<TweetAboutFromLoc, FilterFrom> filter);// Other filter methods}classTwitterByFrom{publicTwitterByAboutFromWhere(Func<TweetAboutLoc, FilterAbout> filter);// Other filter methods // Fields with current filters}Custom syntax trees

11. Query Providers RevisitedBart J.F. De SmetSoftware Development EngineerCloud Programmability Teamdemo

12. Asynchronous Data Access(𝑓 ◦ 𝑔)(𝑥) = 𝑓(𝑔(𝑥)) Way simpler with RxRx is a library for composing asynchronous and event-basedprograms using observable collections.Queries! LINQ!Download at MSDN DevLabs.NET 3.5 SP1 and 4.0, Silverlight 3 and 4

13. JavaScript (RxJS)

14. XNA 3.1 for XBOX and Zune

15. Windows Phone 7Asynchronous Data AccessPush-based data retrievalApplicationGot next?MoveNextInteractiveReactiveOnNextHave next!EnvironmentIObservable<T>IObserver<T>IEnumerable<T>IEnumerator<T>

16. Asynchronous Data AccessEssential interfacesinterfaceIObservable<outT>{IDisposableSubscribe(IObserver<T> observer);}interfaceIObserver<in T>{voidOnNext(T value);voidOnError(Exception ex);voidOnCompleted();}Both interfaces ship in the .NET 4 BCL

17. IQbservable<T>LINQ to WMI EventsHow?ToQbservableTranslatable(Expression trees)IQueryable<T>LINQ to SQLToQueryableLINQ to *.*AsObservableHomo-iconicAsEnumerableAsQbservableAsQueryableToObservableIEnumerable<T>LINQ to ObjectsIObservable<T>LINQ to EventsFixed(MSIL)ToEnumerablePull(interactive)Push(reactive)What?DualityConcurrency(IScheduler)Where?Message loopsDistributedWorker poolsThreads

18. IObservable<T>Asynchronous Data AccessIQbservable<T>interfaceIQbservable<outT> : IObservable<T>{ExpressionExpression { get; }TypeElementType { get; }IQbservableProvider Provider { get; }}interfaceIQbservableProvider{IQbservable<R> CreateQuery<R>(Expression expression);}We welcome semantic discussions.Extended role for some operatorsNo Execute method

19. LINQ to WMI Events (WQL)Bart J.F. De SmetSoftware Development EngineerCloud Programmability Teamdemo

20. Asynchronous Data AccessC# 5.0 and VB 11.0 “await”One versus many?IObservable<T> interface – many resultsTask<T> concrete class – one resultTask<T> based language featureRx bridge by implementing the “await pattern”IAsyncEnumerable<T>

21. Asynchronous Bridge for C# and VB “await”Bart J.F. De SmetSoftware Development EngineerCloud Programmability Teamannouncing

22. Where execution happensIScheduler interfaceSystem.Concurrencyin System.CoreExIntroduction of concurrencyinterfaceIScheduler{DateTimeOffsetNow { get; }IDisposable Schedule(Action action);IDisposable Schedule(Actionaction, TimeSpandueTime);}ToObservableIObservable<T>IEnumerable<T>ToEnumerableSynchronousAsynchronous

23. Where execution happensIScheduler specifies “where”Imported TextBoxTextChangedeventvar res = from word ininput.DistinctUntilChanged() .Throttle(TimeSpan.FromSeconds(0.5))from words in lookup(word)select words;Asynchronous web service callIndicates where things runUse of scheduler to synchronizeres.Subscribe(words => {lst.Items.Clear();lst.Items.AddRange((fromwordinwordsselectword.Word).ToArray());});res.ObserveOn(newControlScheduler(frm)).Subscribe(words => {lst.Items.Clear();lst.Items.AddRange((fromwordinwordsselectword.Word).ToArray());});

24. Where execution happensIScheduler parameterizationBaked in notion of “where”?Entry-point for the schemaCustom schedulers could be very rich (e.g. server farm)varctx = new NorthwindDataContext(); var res = from product inctx.Productswhereproduct.Price > 100mselectproduct.Name;Decoupled “what” from “where”foreach(varproduct inres.RemoteOn(newSqlScheduler(“server”))) // Process product

25. Where execution happensExpression tree remotingRx .NETfromtickerinstockswhereticker.Symbol == “MSFT”selectticker.QuoteObservable data sourceJSON serializerRetargeting to AJAXRxJSstocks.Where(function (t) { returnt.Symbol == “MSFT”; }).Select(function (t) { returnt.Quote; })

26. Remoting of Query OperatorsBart J.F. De SmetSoftware Development EngineerCloud Programmability Teamdemo

27. LINQ to the unexpectedConstraint solvingNon-persistentModel[Decisions[Reals, SA, VZ], Goals[Minimize[20 * SA + 15 * VZ] ],Constraints[ C1 -> 0.3 * SA + 0.4 * VZ >= 2000, C2 -> 0.4 * SA + 0.2 * VZ >= 1500, C3 -> 0.2 * SA + 0.3 * VZ >= 500, C4 -> SA <= 9000, C5 -> VZ <= 6000, C6 -> SA >= 0, C7 -> VZ >= 0 ]]fromminctx.CreateModel(new {vz = default(double), sa = default(double)})where 0.3 * m.sa + 0.4 * m.vz >= 2000 && 0.4 * m.sa + 0.2 * m.vz >= 1500 && 0.2 * m.sa + 0.3 * m.vz >= 500where 0 <= m.sa && m.sa <= 9000 && 0 <= m.vz && m.vz <= 6000orderby 20 * m.sa + 15 * m.vzselectmCost / barrelRefinement %Max # barrelsMin # barrelsTo compute call Solve

28. LINQ to the unexpectedJoining with reactive sourcesObservabledata sourcesfromcostSAinGetPriceMonitor("SA")fromcostVZinGetPriceMonitor("VZ")fromminctx.CreateModel(new { vz = default(double),sa = default(double) })where0.3 * m.sa + 0.4 * m.vz >= 2000 && 0.4 * m.sa + 0.2 * m.vz >= 1500 && 0.2 * m.sa + 0.3 * m.vz >= 500where0 <= m.sa && m.sa <= 9000 && 0 <= m.vz && m.vz <= 6000orderbycostSA* m.sa + costVZ* m.vzselectmSelectManySubscribe here!Parametersto decision

29. Theorem Solving using Z3Bart J.F. De SmetSoftware Development EngineerCloud Programmability Teamdemo