C# 3.0 and LINQ Pavel Yosifovich CTO, Hi-Tech College

Agenda Introduction C# 3.0 New Features Introduction to LINQ LINQ to Objects LINQ to SQL LINQ to XML Summary 2©2008 Pavel Yosifovich

.NET Roadmap YearCLR.NETVisual StudioC# NET 3.0 ext ?

C# 3.0 Features Implicitly Typed Local Variables Automatic Properties Object and Collection Initializers Anonymous Types Extension Methods Lambda Expressions LINQ 4©2008 Pavel Yosifovich

Implicitly Typed Local Variables The var keyword // C# 2.0 int x = 5; string name = "Bart Simpson"; Dictionary data = new Dictionary (); int size = name.Length; // C# 2.0 int x = 5; string name = "Bart Simpson"; Dictionary data = new Dictionary (); int size = name.Length; // C# 3.0 var x = 5; var name = "Bart Simpson"; var data = new Dictionary (); var size = name.Length; var y = x; var keys = data.Keys;// Dictionary.KeyCollection // C# 3.0 var x = 5; var name = "Bart Simpson"; var data = new Dictionary (); var size = name.Length; var y = x; var keys = data.Keys;// Dictionary.KeyCollection 5©2008 Pavel Yosifovich

Automatic Properties public class Person {// C# 2.0 private string _firstName, _lastName; private int _age; public string FirstName { get { return _firstName; } set { _firstName = value; } } public string LastName { get { return _lastName; } set { _lastName = value; } } public int Age { get { return _age; } set { _age = value; } } public class Person {// C# 2.0 private string _firstName, _lastName; private int _age; public string FirstName { get { return _firstName; } set { _firstName = value; } } public string LastName { get { return _lastName; } set { _lastName = value; } } public int Age { get { return _age; } set { _age = value; } } public class Person {// C# 3.0 public string FirstName { get; set; } public string LastName { get; set; } public int Age { get; set; } } public class Person {// C# 3.0 public string FirstName { get; set; } public string LastName { get; set; } public int Age { get; set; } } 6©2008 Pavel Yosifovich

Object Initializers // C# 2.0 Person p = new Person(); p.FirstName = "Bart"; p.LastName = "Simpson"; p.Age = 12; // C# 2.0 Person p = new Person(); p.FirstName = "Bart"; p.LastName = "Simpson"; p.Age = 12; // C# 3.0 Person p = new Person() { FirstName = "Bart", LastName = "Simpson", Age = 12 }; // C# 3.0 Person p = new Person() { FirstName = "Bart", LastName = "Simpson", Age = 12 }; 7©2008 Pavel Yosifovich

Collection Initializers // C# 3.0 List people = new List (); people.Add(new Person() { FirstName = "Bart", LastName = "Simpson", Age = 12 }); people.Add(new Person() { FirstName = "Clark", LastName = "Kent", Age = 35 }); people.Add(new Person() { FirstName = "Peter", LastName = "Parker", Age = 30 }); // C# 3.0 List people = new List (); people.Add(new Person() { FirstName = "Bart", LastName = "Simpson", Age = 12 }); people.Add(new Person() { FirstName = "Clark", LastName = "Kent", Age = 35 }); people.Add(new Person() { FirstName = "Peter", LastName = "Parker", Age = 30 }); // C# 3.0 var people = new List () { new Person() { FirstName = "Bart", LastName = "Simpson", Age = 12 }, new Person() { FirstName = "Clark", LastName = "Kent", Age = 35 }, new Person() { FirstName = "Peter", LastName = "Parker", Age = 30 } }; // C# 3.0 var people = new List () { new Person() { FirstName = "Bart", LastName = "Simpson", Age = 12 }, new Person() { FirstName = "Clark", LastName = "Kent", Age = 35 }, new Person() { FirstName = "Peter", LastName = "Parker", Age = 30 } }; 8©2008 Pavel Yosifovich

Anonymous Types var people = new[] { new { FirstName = "Clark", LastName = "Kent", Age = 36 }, new { FirstName = "Peter", LastName = "parker", Age = 26 }, new { FirstName = "Bart", LastName = "Simpson", Age = 11 } }; foreach (var i in people) Console.WriteLine("{0} {1} ({2})", i.FirstName, i.LastName, i.Age); Console.WriteLine(people[0].GetType().FullName);// ??? var people = new[] { new { FirstName = "Clark", LastName = "Kent", Age = 36 }, new { FirstName = "Peter", LastName = "parker", Age = 26 }, new { FirstName = "Bart", LastName = "Simpson", Age = 11 } }; foreach (var i in people) Console.WriteLine("{0} {1} ({2})", i.FirstName, i.LastName, i.Age); Console.WriteLine(people[0].GetType().FullName);// ??? 9©2008 Pavel Yosifovich

Extension Methods public static class MyExtensions { public static string UpperLower(this string str, bool upperFirst) { StringBuilder newString = new StringBuilder(str.Length); for (int i = 0; i < str.Length; i++) { newString.Append(upperFirst ? char.ToUpper(str[i]) : char.ToLower(str[i])); upperFirst = !upperFirst; } return newString.ToString(); } public static class MyExtensions { public static string UpperLower(this string str, bool upperFirst) { StringBuilder newString = new StringBuilder(str.Length); for (int i = 0; i < str.Length; i++) { newString.Append(upperFirst ? char.ToUpper(str[i]) : char.ToLower(str[i])); upperFirst = !upperFirst; } return newString.ToString(); } string input = Console.ReadLine(); Console.WriteLine("calling extension method for {0}: {1}", input, input.UpperLower(true)); string input = Console.ReadLine(); Console.WriteLine("calling extension method for {0}: {1}", input, input.UpperLower(true)); 10©2008 Pavel Yosifovich

EXTENSION METHODS DEMO

Problem Strongly typed, Intellisense, Compilers, Debuggers (Imperative) Projection, Join, Grouping, Queries (Declarative) Data as Objects Objects as Data 12©2008 Pavel Yosifovich

What is LINQ? Unified programming model for any data type/source –Collections –Database Relational Data –XML Files –Extendable for anything else Introduce more declarative syntax Data is equivalent to Objects 13©2008 Pavel Yosifovich

LINQ enabled ADO.NET LINQ Architecture XML Objects Relational Data.NET Language-Integrated Query (LINQ) 14©2008 Pavel Yosifovich

LINQ Syntax Fundamentals Syntax based on Extension methods Some Extension methods may be replaced by language keywords –where, orderby, select, group, … Auxiliary language features in use –Automatic properties –Anonymous types –Implicitly typed local variables –Object initializers 15©2008 Pavel Yosifovich

LINQ To Objects Working with collections –Any one that implements IEnumerable using System.Linq System.Core.Dll assembly Deferred Execution

LINQ TO OBJECTS DEMO

Classic ADO.NET SqlConnection conn = new SqlConnection(“...“); SqlCommand cmd = conn.CreateCommand(); cmd.CommandText SELECT * FROM Vehicles WHERE Model “Mazda 3“); SqlDataReader r = cmd.ExecuteReader(); while ( r.HasRows ) { Console.WriteLine(r[“Number"] + r[“Year"]); } SqlConnection conn = new SqlConnection(“...“); SqlCommand cmd = conn.CreateCommand(); cmd.CommandText SELECT * FROM Vehicles WHERE Model “Mazda 3“); SqlDataReader r = cmd.ExecuteReader(); while ( r.HasRows ) { Console.WriteLine(r[“Number"] + r[“Year"]); } Application Relational Database No intellisence No compile time checks Loosely bound arguments Untyped Results

LINQ To SQL The DataContext type Custom attributes ( Table, Column ) Not just “Query” Can use stored procedures using System.Data.Linq System.Data.Linq.Dll Assembly

LINQ TO SQL DEMO

LINQ To SQL Performance Performance is good –97% of classic ADO.NET Optimizations –Turn track checking off for reading only ObjectTrackingEnabled = false –Use the DataLoadOptions type to minimize round trips LoadWith<>, AssociateWith<> instance methods –Compile frequently used queries CompiledQuery.Compile (…)

Handling Concurrency Optimistic concurrency mode IsVersion property on Column attribute UpdateCheck property – Always (default) – Never – WhenChanged SubmitChanges argument – FailOnConflict (default) – ContinueOnColflict DataContext has ChangedConflicts ©2008 Pavel Yosifovich22

LINQ To XML New object model –No need to create a document –Very intuitive and flexible using System.Xml.Linq System.Xml.Linq.Dll Assembly Easy to combine with other LINQ providers –E.g. LINQ to SQL

LINQ TO XML DEMO

©2008 Pavel Yosifovich25 Q & A ?

Summary LINQ Allows using data as objects and vice versa Same syntax across any provider C# Language support Use it today!