C# 3.0 & LINQ

1. C# 3.0 & LINQ 2007.11.24 Microsoft Visual C# MVP 한용희 http://blog.naver.com/woom333

2. Agenda • C# 3.0 New Features • Local Variable Type Inference • Object / Collection Initializers • Anonymous Types • Extension Methods • Lambda Expressions • Query Expressions • LINQ • LINQ to SQL • LINQ to XML • LINQ to Entities • LINQ to DataSet

3. Part 1 C# 3.0

4. C# 1.0 , 2.0, 3.0 Expression Trees Partial Classes delegates Object Initializers Accessors Anonymous Methods Reflection Anonymous Classes Nullable Types Object Oriented Lambda Expressions Managed Iterators Extension Methods Type Safety Generics Local Var’s Type Inference Enums LINQ

5. Why C# 3.0

6. New Features • Local Variable Type Inference • Object / Collection Initializers • Anonymous Types • Extension Methods • Lambda Expressions • Query Expressions

7. Local Variable Type Inference inti = 5; string s = "Hello"; double d = 1.0; int[] numbers = new int[] {1, 2, 3}; Dictionary<int,Order> orders = new Dictionary<int,Order>(); var i = 5; var s = "Hello"; var d = 1.0; var numbers = new int[] {1, 2, 3}; var orders = new Dictionary<int,Order>(); “var” means same type as initializer

8. Local Variable Type Inference

9. Object / Collection Initializers public class Point { public int x, y; } Field or property assignments Point a = new Point { x = 0, y = 1}; Point a = new Point(); a.x = 0; a.y = 1;

10. Object / Collection initializers Must implement ICollection<T> List<int> powers = new List<int> { 1, 10, 100, 1000, 10000 }; List<int> powers = new List<int>(); powers.Add(1); powers.Add(10); powers.Add(100); powers.Add(1000); powers.Add(10000);

11. Object / Collection initializers

12. Anonymous Types • Fits with complex temporarily variables var x = new { a = 3, b = 5, c = “some text” }; class __Anonymous1 { private int _a = 3; private int _b = 5; private string _c = “some text”; public int a { get { return v1; } set { _a = value; } } public int b { get { return v2; } set { _b = value; } } public int c { get { return v3; } set { _c = value; } } }

13. Anonymous Types

14. Extension Methods public static class Extensions { public static int ToInt32(this string s) { return Int32.Parse(s); } } string s="1234"; int i = s.ToInt32(); // Same as Extensions.ToInt32(s) • The ability to extend existing types. • Add new functions to existing classes. • No need for editing the existing codes. • Simpler than inheritance. • Inheritance will not work with sealed or primitive types. • Inheritance is limited by class accessibility.

15. Extension Methods

16. Lamda Expressions • Old Programming Concept (λ-calculus). • Exists in most dynamic languages . • Python, Lisp, Ruby • Evolution of anonymous functions. <Delegate Type> identifier = (<param list>) => <Expression> Func<int, int> increment = i => i+1; Increment(10); // result is 11

17. Lamda Expressions delegate stringSomeDelegate(string s); static string TestMethod1(string s) { return s.ToUpper(); } … SomeDelegate d1 = new SomeDelegate(TestMethod1); string a = d1(“abcde"); C# 1.0 C# 2.0 C# 3.0 SomeDelegate d2 = delegate(string s) { return s.ToUpper(); }; string a = d2("abcde"); Implicitly typed SomeDelegate d3 = s => s.ToUpper(); string a = d3("abcde");

18. Lamda Expressions

19. Query Expressions Query expressions var contacts = from c in customers where c.City == “London" select new { c.CustomerID, c.City }; Implicitly typed Local variable Lambda expressions var contacts = customers .Where(c => c.City == “London") .Select(c => new { c.CustomerID, c.City }); Extension methods Anonymous types Object initializers

20. Query Expressions

21. Part 2 Language INtegrated Query(LINQ)

22. Problems Projection, Join, Grouping, Queries (Declarative) OOP, Inheritance, Polymorphism, Loops, Conditions …etc (Imperative)

23. LINQ Project Goals • Unified programming model for any data type • Database Relational Data • XML Files • Collections & Arrays • Introduce more declarative syntax • Helps the system find the best execution strategy • Parallel LINQ (PLINQ)

24. <book> <title/> <author/> <year/> <price/> </book> Relational Objects XML The LINQ Project .NET Language Integrated Query C# 3.0 VB 9.0 Others LINQ toDataSets LINQ toEntities LINQ toSQL LINQ toXML LINQ toObjects

25. LINQ to SQL Accessing data today Queries in quotes SqlConnection c = new SqlConnection(…); c.Open(); SqlCommand cmd = new SqlCommand( @"SELECT c.Name, c.Phone FROM Customers c WHERE c.City = @p0"); cmd.Parameters.AddWithValue("@p0", "London“); DataReader dr = c.Execute(cmd); while (dr.Read()) { string name = dr.GetString(0); string phone = dr.GetString(1); DateTime date = dr.GetDateTime(2); } dr.Close(); Loosely bound arguments Loosely typed result sets No compile time checks

26. LINQ to SQL Accessing data with LINQ to SQL Classes describe data public class Customer { … } public class Northwind: DataContext { public Table<Customer> Customers; … } Tables are like collections Strongly typed connection Northwind db = new Northwind(…); var contacts = from c in db.Customers where c.City == "London" select new { c.Name, c.Phone }; Integrated query syntax Strongly typed results

27. LINQ to SQL Architecture db.Customers.Add(c1); c2.City = “Seattle"; db.Customers.Remove(c3); from c in db.Customers where c.City == "London" select c.CompanyName Enumerate Objects SubmitChanges() SQL Queryor SProc Rows DML or SProcs SQL Server INSERT INTO Customer … UPDATE Customer …DELETE FROM Customer … SELECT CompanyName FROM Customer WHERE City = 'London' Application LINQ to SQL

28. Standard Query Operators

29. LINQ to SQL

30. LINQ to XML Programming XML today Imperative model XmlDocument doc = new XmlDocument(); XmlElement contacts = doc.CreateElement("contacts"); foreach (Customer c in customers) if (c.Country == "USA") { XmlElement e = doc.CreateElement("contact"); XmlElement name = doc.CreateElement("name"); name.InnerText = c.CompanyName; e.AppendChild(name); XmlElement phone = doc.CreateElement("phone"); phone.InnerText = c.Phone; e.AppendChild(phone); contacts.AppendChild(e); } doc.AppendChild(contacts); Document centric No integrated queries Memory intensive <contacts> <contact> <name>Great Lakes Food</name> <phone>(503) 555-7123</phone> </contact> … </contacts>

31. LINQ to XML Programming XML with XLinq Declarative model XElement contacts = new XElement("contacts", from c in customers where c.Country == "USA" select new XElement("contact", new XElement("name", c.CompanyName), new XElement("phone", c.Phone) ) ); Elementcentric Integrated queries Smaller and faster

32. LINQ to XML

33. Guidance for LINQ to Relational Data • LINQ to SQL – Strongly Typed Database • Emphasis on rapid application development • Direct mapping to Microsoft SQL Server family of databases • Release in Microsoft Visual Studio 2008 RTM • LINQ to Entities – Flexible mapping to existing Schema • Focus on enterprise-grade data scenarios • Flexible Mapping to Microsoft SQL Server and third-party databases • Release in Microsoft Visual Studio 2008 update • CTPs on top of Microsoft Visual Studio 2008 Betas/RTM • LINQ to DataSet – In-Memory Cache w/Change Tracking • All the scenarios where DataSet is useful today • Offline, Disconnected, Aggregation • Change Tracking ..Plus support for Query Operations • Strongly typed or Untyped DataSet Support • Release in Microsoft Visual Studio 2008 RTM

34. LINQ to SQLStrongly typed SQL Database • Design Points • Rapid Development against SQL Database • Direct Mapping to SQL Server Schema • Mappings expressed in Attributes or XML file • "Just Work" for common scenarios • Execute when needed • Naming Conventions • Business Logic • Custom Insert/Update/Delete operations • Minimally Intrusive object model • Provide Customization, Optimizations where required • Targets: Microsoft SQL Server • RTM: Microsoft Visual Studio 2008 RTM

35. LINQ to SQLDirect Mapping • Direct Mapping • Each class maps to a single SQL Schema Object • Table, View • Stored Procedure, Table Valued Function • Simple renaming of Tables, Columns • Foreign Keys can be expressed as Relationships • Properties to navigate in query, results • Inheritance • Multiple Classes in a Hierarchy can map to a single Table/View/Stored Proc/TVF with a discriminator column

36. LINQ to SQLFeatures • Customization • Business Logic • Partial classes for generated Objects • Add Methods, non-persistent members, etc. • Business Logic through Partial methods based on naming conventions • Update Logic • Implement partial methods in derived Class • Call Stored Procedures or invoke custom logic • Optimizations • Loading Options • ObjectTrackingEnabled • DeferredLoadingEnabled • Compiled Query • Save overhead of SQL generation from Language Expression

37. Direct Mapping with LINQ to SQL

38. LINQ to EntitiesFlexible Mapping to Relational Data • Design Points • Flexible Mapping to Existing Relational Schema • Well defined Conceptual model • Share common model across products (Reporting, Analysis, etc…) • Declarative Mapping between Application and Store • Allows Storage Schema and Application to evolve independently • Explicit Operations • Server interactions should be explicit • Build implicit logic on top of explicit operations • Common Textual "EntitySQL" Language for Ad-Hoc queries • Targets: Microsoft SQL Server and third-party databases • RTM: Microsoft Visual Studio 2008 Update H1CY08

39. LINQ to EntitiesFlexible Mapping to Relational Data • Flexible Mapping • Mapping a single class to multiple tables/views • Mapping to different types of inheritance • Single Table per Class Hierarchy • Separate Table for each Class in a Hierarchy • Shared Table for Base Class members in a Hierarchy • Complex (composite) types • i.e., Street, City, Region, and Zip as "Address" • Directly mapping Many:Many relationships • Mapping to an arbitrary Query • Store Query • Expose arbitrary store query as a storage Table • Entity Query • Express mapping as EntitySQL against storage schema

40. LINQ to EntitiesFeatures • Customization • Business Logic • Partial Classes, Events, Partial Methods • Update Logic • Generated Update Views • Declarative stored procedures • Optimizations • NoTracking • Extensibility • Partitioning of Metadata • Flexible Runtime Mapping • Metadata Pluggability

41. Flexible Mapping with LINQ to Entities

42. LINQ to DataSetLINQ over Disconnected Cache with Change Tracking • Disconnected Cache • Offline/Remote • Data Aggregation • Application Data All with Change Tracking • Queryable • Filter, Projection • Joins • Across Tables • Other in-Memory sources • Local expressions All through Common LINQ syntax • RTM: Microsoft Visual Studio 2008 RTM

43. LINQ to DataSetTyped and UnTyped • Untyped DataSet • Call AsEnumerable() on DataTable • Reference Fields by Name • Use Field<T>(columnName) • Project out fields for strongly typed result • Typed DataSet • Use strongly typed accessors var query = from row in myDataSet.Tables["Customers"].AsEnumerable() where row .Field<string>("City") == "London" select new { row.Field <string> ("CustomerID"), row.Field <string> ("ContactName") } ; var query = from customer in northwind.Customers where customer.City == "London" select customer;

44. Querying Disconnected Data with LINQ to DataSet