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C# 3.0 and 4.0
- 1. C# 3.0 & 4.0 Buu Nguyen
- 2. Buu Nguyen • Microso6 MVP ASP.NET/IIS 2010, 2011 • Vice President of Technology, KMS Technology • IT Lecturer, RMIT University Vietnam • www.buunguyen.net/blog • @buunguyen
- 3. Agenda • .NET and CLR • EvoluQon of C# • C# 3.0 and LINQ • C# 4.0 and Dynamic Programming
- 4. .NET AND CLR
- 5. .NET Framework C# C++ VB.NET IronRuby ... Visual Studio .NET Common Type System & Common Intermediate Language Common Language Specifica2on Base Class Libraries Common Language Run2me
- 6. CTS and CLS • The Common Type System (CTS) specifies type rules for .NET code. CIL code complies with CTS. • The Common Language SpecificaQon (CLS), a subset of CTS, assures language interoperability.
- 7. CIL • Stack-‐based language • CIL manipulaQon enables – Dynamic code generaQon, e.g. Fasterflect – Code instrumentaQon, e.g. test coverage tools – Decompilers, obfuscators…
- 8. InteresQng Type Concepts • Value types vs. reference types • Stack-‐allocated vs. heap-‐allocated • Pass-‐by-‐value vs. pass-‐by-‐reference • Delegate vs. event types
- 9. More Types Post 1.x • ParQal Types (C# 2.0) • Nullable Types (C# 2.0) • Generic Types (C# 2.0) • Dynamic Types (C# 4.0)
- 10. EVOLUTION OF C#
- 11. C# Language EvoluQon C# 5.0 C# 4.0 Async CaaS Dynamic binding (*) C# 3.0 Named arguments OpQonal parameters LINQ (*) Generic variance Auto-‐ properQes C# 2.0 CollecQon iniQalizer Field-‐like events Robust locking Object iniQalizer Generics (*) Beeer COM interop Anonymous types Nullable types Extension methods Anonymous methods C# 1.0 Yield return ParQal methods Lambda expressions ParQal type Expression trees StaQc class Namespace alias
- 12. DirecQon • Concurrent programming – FuncQonal-‐style programming in C# 3.0 – PLINQ in .NET 4.0 • Dynamic programming – Dynamic binding in C# 4.0 and CaaS in C# 5.0
- 13. C# 3.0
- 14. Features • Implicitly-‐typed Local Variables • Implicitly-‐typed Arrays • Auto-‐implemented ProperQes • Object IniQalizers • CollecQon IniQalizers • ParQal Methods • Anonymous Types • Extension Methods • Lambda Expressions • Expression Trees
- 15. Implicitly-‐typed Local Variables • Benefits – DRY (Don’t Repeat Yourself) • SpecificaQons – Only apply to local variables – Must be iniQalized with an non-‐null expression
- 16. Implicitly-‐typed Arrays • More DRY
- 17. Auto-‐implemented ProperQes • AIP allows us to declare properQes with no implementaQon and no backing fields: compiler will generate code for them automaQcally
- 18. Object IniQalizers • Combine construcQon and property assignments
- 19. CollecQon IniQalizers • Like object iniQalizer, but this Qme applies to collecQons and maps
- 20. ParQal Methods • Method contracts – Work inside parQal classes – Must be private & return void – Can be sta,c or non-‐sta,c – Cannot have out parameter (support ref nonetheless) – Must not be virtual, abstract, override, sealed, or new • Can omit the implementaQon – All calls will be omieed by the compiler
- 21. Anonymous Types • This feature allows us to quickly create objects inside a method without declaring their corresponding class
- 22. Extension Methods • This feature enable us to add methods to exisQng types. This is useful when – We don’t have access to source code of a type – The type is sealed and can’t be inherited
- 23. Lambda Expressions • Shorter form of anonymous methods
- 24. Expression Trees • Code as data – Enable LINQ-‐2-‐SQL, DLR… – Can be compiled to delegate – “Statement trees” are supported in .NET 4.0
- 25. LINQ
- 26. Show me some LINQ! var people = from p in GetSalesPeople() where p.HireDate > hireDate select p; foreach (SalesPerson person in people) { Console.WriteLine(person.FirstName); }
- 27. LINQ in a Nutshell Integrate query expressions into languages Unified approach to query data Declara2ve style of coding Extensible via provider mechanism
- 28. How is LINQ Implemented? • LINQ Query Expressions are translated to normal invocaQons to Standard Query Operators var contacts = from c in customers where c.State == "WA" select new { c.Name, c.Phone }; var contacts = customers .Where(c => c.State == "WA") .Select(c => new { c.Name, c.Phone });
- 29. LINQ & C# 3.0 var contacts = from c in customers Query Expression where c.State == "WA" select new { c.Name, c.Phone }; Implicitly-typed Local Variable Lambda Expression var contacts = customers .Where(c => c.State == "WA") .Select(c => new { c.Name, c.Phone }); Extension Object Method Initializer Anonymous Type
- 30. Where Do SQOs Come From? § Extensions methods for IEnumerable<T> defined in System.Linq.Enumerable § Building a LINQ-‐enabled data source is as simple as having your class implemenQng IEnumerable<T>
- 31. LINQ Clauses from let where join select orderby group
- 32. Structure of LINQ Queries First Line • from clause Middle Lines • from, where, orderby, join, let clauses Last Line • select or group-by clause
- 33. LINQ Architecture Visual Basic C# Others… .NET Language-Integrated Query LINQ to ADO.NET LINQ LINQ LINQ LINQ LINQ to XML to Object to SQL to DataSet to Entities <book> <Qtle/> <author/> <year/> <price/> </book> Objects RelaQonal DB XML
- 34. IEnumerable<T> from itemName in srcExpr Object where predExpr Object orderby (keyExpr (ascending | descending)) Object Objects in Memory select selExpr ... where where orderby where orderby select
- 35. IQueryable<T> Nothing In from itemName in srcExpr where predExpr orderby (keyExpr (ascending | descending)) Memory select selExpr ... “FROM [srcExpr] WHERE ...” where FROM [srcExpr] WHERE predExpr where ORDER BY [keyExpr]” orderby SELECT [selExpr] where FROM [srcExpr] WHERE predExpr ORDER BY [keyExpr]” orderby select
- 36. Deferred vs. Non-‐deferred Operators Deferred Non-‐deferred • Rule of thumb: LINQ query syntax • Rule of thumb: scalar/single-‐value or IEnumerable<T> return return or conversion • AsEnumerable, Cast, • Aggregate, All, Any, Concat, DefaultIfEmpty, Average, Contains, Count, Distinct, Empty, Except, ElementAt, GroupBy, GroupJoin, ElementAtOrDefault, Last, Intersect, Join, OfType, LastOrDefault, LongCount, OrderBy, Max, Min, Single, OrderByDescending, Range, SingleOrDefault, Sum, Repeat, Reverse, Select, ToArray, ToDictionary, SelectMany, Skip, ToList, ToLookup SkipWhile, Take, TakeWhile, ThenBy, ThenByDescending, Union, Where 36
- 37. C# 4.0
- 38. Features Covered • OpQonal Parameters • Named Arguments • Beeer COM Interop • Generic Variance • Robust Locking • Field-‐like Events
- 40. How to implement MailMessage()?
- 41. Overloading
- 43. OpQonal Values • Numeric and string literals • null • Compile-‐Qme constants • Enum members • default(T) • Parameterless constructor for structs
- 44. RestricQons • OpQonal parameters must come a6er required parameters – Except for parameter array (empty array is used when not specified) • OpQonal parameters can’t be ref or out
- 45. In Depth: DefiniQon Site
- 46. In Depth: Call Site
- 47. Consequence • OpQonal values are part of the published API, if they are changed, client code must be recompiled. Worse, the compiler won’t warn you if you don’t change.
- 48. NAMED ARGUMENTS
- 49. How to Avoid the Comments?
- 51. Named Arguments
- 52. …Named Arguments
- 53. RestricQons • PosiQonal arguments must come before named arguments
- 54. Under the Hood • The compiler just reorders, that’s all
- 55. Consequence • Parameter names are part of the published API, if they are changed, client code must be changed.
- 57. How Do You Like This?
- 58. #1: Omit ref
- 60. GENERIC VARIANCE
- 61. Is This Okay?
- 62. No, because…
- 63. Generic Covariance • Generic covariance reserves assignment compaQbility on generic types – If T1 is a subtype of T2, GT<T1> behaves like subtype of GT<T2> on assignment • Safe only when GT doesn’t “take in” any T
- 64. Example
- 65. On Delegate
- 66. Is This Okay?
- 67. No, because…
- 68. Generic Contravariance • Generic covariance reverses assignment compaQbility on generic types – If T1 is a subtype of T2, GT<T1> behaves like supertype of GT<T2> on assignment • Safe only when GT doesn’t return any T
- 69. Example
- 70. On Delegate
- 71. Under the Hood
- 72. ROBUST LOCKING
- 73. Problem If the thread is aborted a>er the lock is acquired but before we enter the try block, we won’t have released the lock.
- 74. SoluQon
- 76. The Problem Lock on ‘this’ is bad. Lock on ‘type’ is bad.
- 77. The SoluQon A simple lock would work, but this is beeer because it’s lock-‐free.
- 78. DYNAMIC BINDING
- 79. WHAT IS DYNAMIC BINDING
- 80. StaQc vs. Dynamic Binding Sta2c Binding Dynamic Biding • Compiler figures out which • All bindings happen during members to call (binding run Qme process) – Defer subtype polymorphic resoluQon Qll run Qme
- 81. StaQc Binding
- 82. Benefits of StaQc Binding • Type and name errors are detected at compile Qme, e.g. – Invoke non-‐existent members – Pass in arguments with wrong type – Perform illegal cast
- 83. Dynamic Binding
- 84. HOW IS IT IMPLEMENTED?
- 85. Run Time Binding • Instead of aeempQng binding and generaQng CIL, the compiler packages the call and sends it to the Dynamic Language RunQme • At run Qme, the DLR performs binding and execuQon
- 86. Under the Hood becomes
- 87. The Dynamic Language RunQme
- 88. Process in a nutshell C# dynamic Dynamic builds Objects User-‐defined or from other languages compiled uses IDynamicMetaObjectProvider Call Sites cached Delegate Expression emits Tree DLR C# Binder builds
- 89. Dynamic Type in CIL
- 90. WHEN DO WE NEED IT?
- 91. Key Scenarios 1. Access a member with only knowledge of its name, arguments, and target object 2. Interop with dynamic languages, e.g. IronRuby, IronPython 3. Have the target object decide how to respond to a call at run Qme
- 92. Key Scenarios 1. Access a member with only knowledge of its name, arguments, and target object 2. Interop with dynamic languages, e.g. IronRuby, IronPython 3. Have the target object decide how to respond to a call at run Qme
- 93. Access Members
- 94. ReflecQon
- 95. Dynamic Type
- 96. Single vs. MulQple Dispatch Single Dispatch Mul2ple Dispatch • Method is selected based • Method is selected based on the runQme type of the on both the runQme type of target object the target object and those of the method’s arguments
- 97. Dispatch Example
- 98. Key Scenarios 1. Access a member with only knowledge of its name, arguments, and target object 2. Interop with dynamic languages, e.g. IronRuby, IronPython 3. Have the target object decide how to respond to a call at run Qme
- 99. Invoke Ruby Code
- 100. Work with Ruby Class
- 102. Key Scenarios 1. Access a member with only knowledge of its name, arguments, and target object 2. Interop with dynamic languages, e.g. IronRuby, IronPython 3. Have the target object decide how to respond to a call at run Qme
- 103. The Magic Interface IDynamicMetaObjectProvider ExpandoObject DynamicObject
- 104. ExpandoObject
- 105. DynamicObject’s OperaQons Name Descrip2on TryGetMember Member geeer, e.g. obj.Name TrySetMember Member seeer, e.g. obj.age = 10 TryDeleteMember Member removal (no equivalent in C#) TryInvokeMember Method invocaQon, e.g. obj.Invoke() TryConvert CasQng, e.g. (int)obj TryCreateInstance Object creaQon (no equivalent in C#) TryInvoke Self invocaQon, e.g. obj(10) TryBinaryOperaQon Binary operaQon, e.g. obj + 10 TryUnaryOperaQon Unary operaQon, e.g. !obj TryGetIndex Indexer geeer, e.g. obj[“key”] TrySetIndex Indexer seeer, e.g. obj[“key”] = value TryDeleteIndex Indexer removal (no equivalent in C#)
- 106. Log Seeers & InvocaQons
- 107. StaQcInvoker
- 108. StaQcInvoker
- 109. Close to the metal
- 110. …Close to the metal
- 111. …Close to the metal
- 112. RESTRICTIONS
- 113. RestricQon #1 • Doesn’t work with extension methods
- 114. RestricQon #2 • Can’t resolve staQc members or constructors on a dynamic type
- 115. RestricQon #3 • Method groups, anonymous methods and lambda expressions to be casted to exact type
- 116. RestricQon #4