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Agenda Impedance Mismatch C# 3.0 New Features Introduction to LINQ LINQ to Objects LINQ to SQL LINQ to XML Summary

Impedance Mismatch Incompatibility between systems. Describes an inadequate ability of one system to accommodate input from another.

Introduction RDBMS Business Logic Windows UI Web UI Console Web Service Windows Service Impedance Mismatch Data Access

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

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

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# 3.0 public string FirstName { get; set; } public string LastName { get; set; } public int Age { get; set; } }

Object Initializers // 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 };

Collection Initializers // C# 3.0 List<Person> people = new List<Person>(); 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<Person>() { new Person() { FirstName = "Bart", LastName = "Simpson", Age = 12 }, new Person() { FirstName = "Clark", LastName = "Kent", Age = 35 }, new Person() { FirstName = "Peter", LastName = "Parker", Age = 30 } };

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); // ??? In which the type name is generated by the compiler and Is not available at the source code level.

Extension Methods Extension methods allows us to “add” method to existing types without creating a new derived type, recompiling, or otherwise modifying the original type. Extension methods are a special kind of “static” method, but they are called as if they were instance methods. The first parameter specifies which type the method operates on, and the parameter is preceded by the “this” modifier.

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(); } } string input = Console.ReadLine(); Console.WriteLine("calling extension method for {0}: {1}", input, input. UpperLower (true));

Lambda Expressions A lambda expression is an anonymous function that can contain expressions and statements, and can be used to create delegates or expression tree types. var x => x+1; //Implicitly typed expression. var x => { return x+1;} //Implicitly type statement. int x => x+1; //Explicitly typed expression. int x => {return x+1;} //Explicitly type statement.

var prs = Process.GetProcesses() .Where(process => process.WorkingSet64 > 20 * 1024 * 1024) .OrderByDescending(process => process.WorkingSet64) .Select(process => new { process.Id, Name = process.ProcessName }); Extension methods Local variable type inference Anonymous types Object initializers Lambda expressions Language Extensions

Introduction to LINQ What is LINQ? Stands for Language INtegrated Query Allows developers to query data structures using SQL-like syntax from within their application’s code Is available to both C# and Visual Basic developers in Visual Studio 2008

The LINQ Project C# 3.0 Visual Basic 9.0 Others .NET Language Integrated Query

LINQ to Objects C# 3.0 Visual Basic 9.0 Others .NET Language Integrated Query

LINQ to Object example LINQ Example - Querying an array //Create an array of integers int [] myarray = new int [] { 49, 28, 20, 15, 25, 23, 24, 10, 7, 34 }; //Create a query for odd numbers var oddNumbers = from i in myarray where i % 2 == 1 select i; //Display the results of the query foreach ( int i in oddNumbers) Console .WriteLine(i); //Create a query for odd numbers, sorted var oddNumbers = from i in myarray where i % 2 == 1 orderby i select i; //Create a query for odd numbers, sorted in descending order var oddNumbers = from i in myarray where i % 2 == 1 orderby i descending select i; //Create a query for odd numbers var oddNumbers = from i in myarray where i % 2 == 1 select i; //Compose the original query to create a query for odd numbers var sorted = from i in oddNumbers orderby i descending select i;

LINQ to Objects Native query syntax in C# and VB IntelliSense Autocompletion Query Operators can be used against any .NET collection (IEnumerable<T>) Select, Where, GroupBy, Join, etc. Deferred Query Evaluation Lambda Expressions using System; using System.Query; using System.Collections.Generic; class app { static void Main() { string [] names = { "Allen", "Arthur", "Bennett" }; IEnumerable < string > ayes = names .Where(s => s[0] == 'A'); foreach ( string item in ayes) Console .WriteLine(item); names[0] = "Bob"; foreach ( string item in ayes) Console .WriteLine(item); } } Arthur using System; using System.Query; using System.Collections.Generic; class app { static void Main() { string [] names = { "Allen", "Arthur", "Bennett" }; IEnumerable < string > ayes = names .Where(s => s[0] == 'A'); foreach ( string item in ayes) Console .WriteLine(item); names[0] = "Bob"; foreach ( string item in ayes) Console .WriteLine(item); } } Allen Arthur using System; using System.Query; using System.Collections.Generic; class app { static void Main() { string [] names = { "Burke", "Connor", "Frank", "Everett", "Albert", "George", "Harris", "David" }; IEnumerable < string > expr = from s in names where s.Length == 5 orderby s select s.ToUpper(); foreach ( string item in expr) Console .WriteLine(item); } } BURKE DAVID FRANK using System; using System.Query; using System.Collections.Generic; class app { static void Main() { string [] names = { "Burke", "Connor", "Frank", "Everett", "Albert", "George", "Harris", "David" }; Func < string , bool > filter = s => s.Length == 5; Func < string , string > extract = s => s; Func < string , string > project = s = s.ToUpper(); IEnumerable < string > expr = names .Where(filter) .OrderBy(extract) .Select(project); foreach ( string item in expr) Console .WriteLine(item); } } BURKE DAVID FRANK

LINQ to SQL C# 3.0 Visual Basic 9.0 Others .NET Language Integrated Query

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

LINQ to SQL Maps .NET classes to relational SQL data Translates LINQ queries to SQL execution Supports change tracking for insert, update, delete operations Built on top of ADO.NET and integrates with connection-pooling and transactions

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

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

Language Extensions var contacts = from c in dc.GetTable<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 }); Extension methods Lambda expressions Query expressions Object initializers Anonymous types Local variable type inference

LINQ to XML C# 3.0 Visual Basic 9.0 Others .NET Language Integrated Query

LINQ to XML Large Improvement Over Existing Model Declarative Model Supports: Creating XML Loading & querying XML Modifying & saving XML

LINQ to XML 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); Programming XML today <contacts> <contact> <name>Great Lakes Food</name> <phone>(503) 555-7123</phone> </contact> … </contacts> Imperative model Document centric No integrated queries Memory intensive

LINQ to XML 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) ) ); Programming XML with LINQ Declarative model Element centric Integrated queries Smaller and faster

Summary LINQ will be a really important technology. Native query integration within languages improves productivity and error checking. Using LINQ with ASP.NET is both easy and fun. ASP.Net + LINQ - a simple and powerful way to build data driven web applications.

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