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DISTRIBUTED SYSTEMS RESEARCH GROUP

http://nenya.ms.mff.cuni.cz

CHARLES UNIVERSITY PRAGUE

Faculty of Mathematics and Physics

C# 3.0 and .NET 3.5: A BriefOverview

Pavel Jeek

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Pavel Jeek

C# 3.0 and .NET 3.5

C# 3.0 Features

Implicitly Typed Local Variables Extension Methods

Lambda Expressions

Object Initializers

Collection Initializers

Anonymous Types

Expression Trees

Query Expressions

Beta versions of C# 3.0 compiler, libraries and Visual Studio 2005integration can be downloaded at:http://download.microsoft.com/download/4/7/0/4703eba2-78c4-4b09-8912-69f6c38d3a56/linq%20preview.msi

.NET Framework 3.5 Beta 1:http://www.microsoft.com/downloads/details.aspx?FamilyId=E3715E6F-E123-428B-8A0F-028AFB9E0322&displaylang=en

Visual Studio code name Orcas Beta 1:http://msdn2.microsoft.com/en-us/vstudio/aa700831.aspx

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Implicitly Typed Local Variables

Examples:var i = 5;var s = "Hello";var d = 1.0;var numbers = new int[] {1, 2, 3};var orders = new Dictionary();

Are equivalent to:int i = 5;string s = "Hello";double d = 1.0;int[] numbers = new int[] {1, 2, 3};Dictionary orders = new Dictionary();

Errors:

var x; // Error, no initializer to infer type fromvar y = {1, 2, 3}; // Error, collection initializer not permittedvar z = null; // Error, null type not permitted

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Extension Methods

Declaration:public static partial class Extensions {

public static int ToInt32(this string s) {

return Int32.Parse(s);

}

}

Usage:

string s = "1234";

int i = s.ToInt32(); // Same as Extensions.ToInt32(s)

Instance methods take precedence over extension methods Extension methods imported in inner namespace declarations take

precedence over extension methods imported in outer namespace

declarations

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Extension Methods (2)

Declaration:public static partial class Extensions {

public static T[] Slice(this T[] source, int index, int count) {if (index < 0 || count < 0 || source.Length index < count)

throw new ArgumentException();T[] result = new T[count];Array.Copy(source, index, result, 0, count);return result;

}}

Usage:

int[] digits = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};

int[] a = digits.Slice(4, 3); // Same as Extensions.Slice(digits, 4, 3)

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C# 3.0 and .NET 3.5

Lambda Expressions Example of C# 2.0 anonymous method:

class Program {delegate T BinaryOp(T x, T y);

static void Method(BinaryOp op, T p1, T p2) {

Console.WriteLine(op(p1, p2));

}

static void Main() {

Method(delegate(int a, int b) { return a + b; }, 1, 2);}

}

C# 3.0 lambda expressions provide further simplification:

class Program {

delegate T BinaryOp(T x, T y);

static void Method(BinaryOp op, T p1, T p2) {

Console.WriteLine(op(p1, p2));}

static void Main() {Method((a, b) => a + b, 1, 2);

}}

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Pavel Jeek

C# 3.0 and .NET 3.5

Lambda Expressions (2)

Expression or statement body Implicitly or explicitly typed parameters

Examples:x => x + 1 // Implicitly typed, expression body

x => { return x + 1; } // Implicitly typed, statement body

(int x) => x + 1 // Explicitly typed, expression body

(int x) => { return x + 1; } // Explicitly typed, statement body(x, y) => x * y // Multiple parameters

() => Console.WriteLine() // No parameters

A lambda expression is a value, that does not have a type but can beimplicitly converted to a compatible delegate type

delegate R Func(A arg);

Func f1 = x => x + 1; // Ok

Func f2 = x => x + 1; // Ok

Func f3 = x => x + 1; // Error double cannot be// implicitly converted to int

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Lambda expressions participate in inference process of typearguments of generic methods

In initial phase, nothing is inferred from arguments that are lambda

expressions

Following the initial phase, additional inferences are made from

lambda expressions using an iterative process

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Generic extension method example:public class List : IEnumerable, { }

public static class Sequence {

public static IEnumerable Select(

this IEnumerable source,

Func selector)

{

foreach (T element in source) yield return selector(element);

}

}

Calling extension method with lambda expression:

List customers = GetCustomerList();

IEnumerable names = customers.Select(c => c.Name);

Rewriting extension method call:

IEnumerable names = Sequence.Select(customers, c => c.Name);

T type argument is inferred to Customer based on source argument type

Sequence.Select(customers, c => c.Name)

c lambda expression argument type is infered to Customer

Sequence.Select(customers, (Customer c) => c.Name)

S type argument is inferred to string based on return value type of the lambda expression

Sequence.Select(customers, (Customer c) => c.Name)

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Pavel Jeek

C# 3.0 and .NET 3.5

Object Initializers

Class representing a point:public class Point {

private int x, y;

public int X { get { return x; } set { x = value; } }

public int Y { get { return y; } set { y = value; } }

}

New instance can be created using object initializer:

var a = new Point { X = 0, Y = 1 };

Which is equivalent to:

var a = new Point();

a.X = 0;

a.Y = 1;

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Pavel Jeek

C# 3.0 and .NET 3.5

Object Initializers (2)

Class representing a rectangle:

public class Rectangle {private Point p1, p2;

public Point P1 { get { return p1; } set { p1 = value; } }

public Point P2 { get { return p2; } set { p2 = value; } }

}


var r = new Rectangle {P1 = new Point { X = 0, Y = 1 },

P2 = new Point { X = 2, Y = 3 }

};


var r = new Rectangle();

var __p

1 = new Point();__p1.X = 0;

__p1.Y = 1;

r.P1 = __p1;

var __p2 = new Point();

__p2.X = 2;

__p2.Y = 3;

r.P2 = __p2;

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Pavel Jeek

C# 3.0 and .NET 3.5

Object Initializers (3)

Class representing a rectangle with constructor that allocates p1 and p2:public class Rectangle {

private Point p1 = new Point();

private Point p2 = new Point();

public Point P1 { get { return p1; } }

public Point P2 { get { return p2; } }

}


var r = new Rectangle {

P1 = { X = 0, Y = 1 },

P2 = { X = 2, Y = 3 }

};


var r = new Rectangle();

r.P1.X = 0;

r.P1.Y = 1;

r.P2.X = 2;

r.P2.Y = 3;

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Pavel Jeek

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Collection Initializers

Example:List digits = new List { 0, 1, 2};

Is equivalent to:

List digits = new List();

digits.Add(0);

digits.Add(1);digits.Add(2);

List has to implement System.Collections.Generic.ICollection interface with

the Add(T) method

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Combining Object and Collection Initializers Class representing a contact with name and list of phone numbers:

public class Contact {private string name;private List phoneNumbers = new List();

public string Name { get { return name; } set { name = value; } }public List PhoneNumbers { get { return phoneNumbers; } }

}

List of contacts can be created and initialized with:var contacts = new List {

new Contact {

Name = "Chris Smith",PhoneNumbers = { "206-555-0101", "425-882-8080" }

},

new Contact {Name = "Bob Harris",PhoneNumbers = { "650-555-0199" }

}};

Which is equivalent to:var contacts = new List();var __c1 = new Contact();__c1.Name = "Chris Smith";

__c1.PhoneNumbers.Add("206-555-0101");__c1.PhoneNumbers.Add("425-882-8080");contacts.Add(__c1);var __c2 = new Contact();__c2.Name = "Bob Harris";__c2.PhoneNumbers.Add("650-555-0199");contacts.Add(__c2);

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Pavel Jeek

C# 3.0 and .NET 3.5

Anonymous Types

Following expression:new { p1 = e1 , p2 = e2 , pn = en }

Can be used to define an anonymous type :

class __Anonymous1 {

private T1 f1 ;

private T2 f2 ;

private Tn fn ;

public T1 p1 { get { return f1 ; } set { f1 = value ; } }



}

And create its instance using object initializer

Different anonymous object initilizers that define properties with same names in the same ordergenerate the same anonymous type:

var p1 = new { Name = "Lawnmower", Price = 495.00 };

var p2 = new { Name = "Shovel", Price = 26.95 };

p1 = p2;

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Pavel Jeek

C# 3.0 and .NET 3.5

Expression Trees

Permit lambda expressions to be represented as data structures instead ofexecutable code

Lambda expression convertible to delegate D (assignment causes code generation)

is also convertible to expression tree (abstract syntax tree) of type

System.Query.Expression (assignment causes expression tree generation)

Func f = x => x + 1; // Code

Expression e = x => x + 1; // Data

Full specification is not available yet (May 2006)

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C# 3.0 and .NET 3.5

ADO.NET: Connection-oriented Access

1.) Declare connectiontry {

1.) Request connection to database

3.) Process result

2.) Execute SQL commands

4.) Release Resources

} catch ( Exception ) {

Handle exception

} finally {

try {4.) Close connection

} catch (Exception)

{ Handle exception }

}

University of Linz, Institute for System Software, 2004

published under the Microsoft Curriculum License(http://www.msdnaa.net/curriculum/license_curriculum.aspx)

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ADO.NET Example: EmployeeReader (1)

using System;

using System.Data;using System.Data.OleDb;

public class EmployeeReader {

public static void Main() {

string connStr = "provider=SQLOLEDB; data source=(local)\\NetSDK; " +"initial catalog=Northwind; user id=sa; password=; ";

IDbConnection con = null; // declare connection object

try {

con = new OleDbConnection(connStr); // create connection object

con.Open(); // open connection

1) Declare and request connection to database

// create SQL command

IDbCommand cmd = con.CreateCommand();

cmd.CommandText = "SELECT EmployeeID, LastName, FirstName +

FROM Employees";

// execute SQL command; result is an OleDbDataReader

IDataReader reader = cmd.ExecuteReader();

2) Execute SQL commands



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Pavel Jeek

C# 3.0 and .NET 3.5

ADO.NET Example: EmployeeReader (2)

IDataReader reader = cmd.ExecuteReader();object[] dataRow = new object[reader.FieldCount];

while (reader.Read()) {

int cols = reader.GetValues(dataRow);

for(int i = 0; i < cols; i++) Console.Write("| {0} " , dataRow[i]);

Console.WriteLine();

}

3) Read and process data rows

reader.Close();

} catch (Exception e) {

Console.WriteLine(e.Message);

} finally {

try {

if(con != null)

// ----- close connection

con.Close();

} catch (Exception ex) { Console.WriteLine(ex.Message); }

} } }

4) Release resources and close connection



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Pavel Jeek

C# 3.0 and .NET 3.5

Query Expressions

Query expressions or LINQ (Language INtergrated Queries) are the key feature of.NET 3.5

Query expressions are translated to method calls works on classes like:

delegate R Func(A arg);

class C

{

public C Where(Func predicate);

public C Select(Func selector);

public C SelectMany(Func selector);public O OrderBy(Func keyExpr);

public O OrderByDescending(Func keyExpr);

public C GroupBy(Func keyExpr);

p

ublic C Group

By(Func keyExp

r, FuncelemExpr);

}

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Pavel Jeek

C# 3.0 and .NET 3.5

Query Expressions Examples

Query expression:

from c in customers where c.City == "London select c

Gets translated to:

customers.Where(c => c.City == "London")

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Pavel Jeek

C# 3.0 and .NET 3.5


Query expression:

from c in customers where c.City == "London select c.Name

Gets translated to:

customers.Where(c => c.City == "London").Select(c => c.Name)

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C# 3.0 and .NET 3.5


Query expression:

from c in customers orderby c.Name select new { c.Name, c.Phone }

Gets translated to:

customers.OrderBy(c => c.Name).Select(c => new { Name = c.Name,Phone = c.Phone })

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C# 3.0 and .NET 3.5


Query expression:

from c in customers

where c.City == "London"

from o in c.Orders

where o.OrderDate.Year == 2005

select new { c.Name, o.OrderID, o.Total }

Gets translated to:

customers.Where(c => c.City == "London").

SelectMany(c =>

c.Orders.

Where(o => o.OrderDate.Year == 2005).Select(o => new {

Name = c.Name, OrderID = o.OrderID, Total = o.Total})

)

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C# 3.0 and .NET 3.5

BCL Extended by Query Expressions

Set of generic extension methods (Select, Where, OrderBy, + others) implemented for IEnumerable

interface, example:

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

var numberGroups = fromn in numbers group nby n % 5 into g

select new {Remainder = g.Key, Numbers = g.Group};

foreach (var g in numberGroups) {

Console.WriteLine("Numbers with a remainder of {0} when divided by 5:", g.Remainder);

);

foreach (int n in g.Numbers) {

Console.WriteLine(n);

}

}

DLinq Classes for SQL data access using query expressions

XLinq - Classes for XML data access using query expressions

Numbers with a remainder of 0 when divided by 5:

5

0Numbers with a remainder of 4 when divided by 5:

4

9

Numbers with a remainder of1 when divided by 5:

1

6

Numbers with a remainder of3 when divided by 5:

3

8

Numbers with a remainder of 2 when divided by 5:

72

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Pavel Jeek

C# 3.0 and .NET 3.5

DLinq Creating Entity Classes

Only instances of entity classes, i.e. entities , can be stored in/retrieved from databases

[Table] // Table is named Customerpublic class Customer

{

public string CustomerID; // Transient data not stored in DB

public string City; // Transient data not stored in DB}

[Table(Name="Customers")]

public class Customer{

public string CustomerID; // Transient data not stored in DB

public string City; // Transient data not stored in DB}

[Table(Name="Customers")]public class Customer

{

[Column(Id=true)] // Part of database primary keypublic string CustomerID;

[Column]

public string City;

}

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DLinq - DataContext

DataContextis equivalent of ADO.NET connection

It retrieves data (objects) from the database and submits changes

It translates requests (queries) for objects into SQL queries

Using the DataContext to retrieve customer objects whose city is London:

// DataContext takes a connection string

DataContext db = new DataContext("c:\\northwind\\northwnd.mdf");

// Get a typed table to run queriesTable Customers = db.GetTable();

// Query for customers from Londonvar q = from c in Customers where c.City == "London select c;

foreach (var cust in q) {Console.WriteLine("id = {0}, City = {1}", cust.CustomerID,cust.City);

}

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Pavel Jeek

C# 3.0 and .NET 3.5

DLinq Strongly Typed DataContext

p

ublicp

artial class Northwind : DataContext{

public Table Customers;

public Table Orders;

public Northwind(string connection): base(connection) {}

}

Retrieving customer objects whose city is London more easily:

Northwind db = new Northwind("c:\\northwind\\northwnd.mdf");

var q = from c in db.Customers where c.City == "London select c;

foreach (var cust in q) {

Console.WriteLine("id = {0}, City = {1}",cust.CustomerID,cust.City);}

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Pavel Jeek

C# 3.0 and .NET 3.5

DLinq Query Execution

Queries are not imperative they are not executed immediately

var q = from c in db.Customerswhere c.City == "London"select c;

Only creates an instance ofQuery type and assigns it to q

When the application tries to enumerate the contents of a query, it gets executed

(i.e. deferred execution):

// Execute first timeforeach (Customer c in q) Console.WriteLine(c.CompanyName);

// Execute second time

foreach (Customer c in q) Console.WriteLine(c.CompanyName);

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Pavel Jeek

C# 3.0 and .NET 3.5

DLinq Advantage of Deferred Execution

Partial query contruction:


if (orderByLocation) {

q = from c in qorderby c.Country, c.Cityselect c;

} else if (orderByName) {

q = from c in qorderby c.ContactNameselect c;

}

foreach (Customer c in q) Console.WriteLine(c.CompanyName);

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Pavel Jeek

C# 3.0 and .NET 3.5

DLinq Avoiding Deferred Execution

Query can be converted to standard collection classes using ToList() orToArray() Standard Query Operators (or converted to DataSets DataTable usingToDataTable()) leads to immediate execution:


// Execute once using ToList(), ToArray() or ToDataTable()var list = q.ToList();

foreach (Customer c in list) Console.WriteLine(c.CompanyName);

foreach (Customer c in list) Console.WriteLine(c.CompanyName);

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Pavel Jeek

C# 3.0 and .NET 3.5

DLinq Defining Relationships

[Table(Name="Customers")]

public class Customer{

[Column(Id=true)]public string CustomerID;...private EntitySet _Orders;[Association(Storage="_Orders", OtherKey="CustomerID")]

public EntitySet Orders {get { return this._Orders; }

set { this._Orders.Assign(value); }}

}

[Table(Name="Orders")]public class Order{

[Column(Id=true)]

public int OrderID;

[Column]public string CustomerID;

private EntityRef _Customer;

[Association(Storage="_Customer", ThisKey="CustomerID")]public Customer Customer {

get { return this._Customer.Entity; }set { this._Customer.Entity = value; }

}}

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Pavel JeekC# 3.0 and .NET 3.5

DLinq Querying Across Relationships

Query using the Orders property to form the cross product between customers andorders, producing a new sequence of Customer and Order pairs:

var q = from c in db.Customersfrom o in c.Orderswhere c.City == "London"select new { c, o };

Another query producing the same result:

var q = from o in db.Orderswhere o.Customer.City == "London"select new { c = o.Customer, o };

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DLinq Modifying Entities

Northwind db = new Northwind("c:\\northwind\\northwnd.mdf");

// Query for a specific customerstring id = "ALFKI";

var cust = db.Customers.Single(c => c.CustomerID == id);

// Change the name of the contactcust.ContactName = "New Contact";

// Delete an existing Order

Order ord0 = cust.Orders[0];

// Removing it from the table also removes it from the Customers listdb.Orders.Remove(ord0);

// Create and add a new Order to Orders collection

Order ord = new Order { OrderDate = DateTime.Now };cust.Orders.Add(ord);

// Ask the DataContext to save all the changes generates appropriate SQL command

db.SubmitChanges();

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DLinq Creating Simple Databases

[Table(Name="DVDTable")]

public class DVD{

[Column(Id = true)]public string Title;[Column]public string Rating;

}

public class MyDVDs : DataContext

{public Table DVDs;public MyDVDs(string connection) : base(connection) {}

}

// Creating a new databaseMyDVDs db = new MyDVDs("c:\\mydvds.mdf");db.CreateDatabase();

// Replacing an existing oneMyDVDs db = new MyDVDs("c:\\mydvds.mdf");

if (db.DatabaseExists()) {db.DeleteDatabase();

}

db.CreateDatabase();

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DLinq Inheritance

[Table]

[InheritanceMapping(Code = "C", Type = typeof(Car))][InheritanceMapping(Code = "T", Type = typeof(Truck))]

[InheritanceMapping(Code = "V", Type = typeof(Vehicle), IsDefault = true)]public class Vehicle {

[Column(IsDiscriminator = true)]public string Key;[Column(Id = true)]public string VIN;[Column]

public string MfgPlant;}

public class Car : Vehicle {[Column]public int TrimCode;[Column]public string ModelName;

}

public class Truck : Vehicle {

[Column]public int Tonnage;[Column]public int Axles;

}

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DLinq Inheritance

Example queries:

var q = db.Vehicle.Where(p => p is Truck);

var q = db.Vehicle.OfType();

var q = db.Vehicle.Select(p => p as Truck).Where(p => p != null);foreach (Truck p in q)

Console.WriteLine(p.Axles);

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DLinq Query Visualizer in VS

static void Main(string[] args) {Northwnd db = new Northwnd(@"C:\program files\linq preview\data\northwnd.mdf");

var q =from c in db.Customerswhere c.City == "London"select c;

} // Breakpoint

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XLinq Example XML

Patrick Hines206-555-0144425-555-0145

123 Main StMercer IslandWA68042

10

Gretchen Rivas206-555-0163

123 Main StMercer IslandWA68042

11

Scott MacDonald925-555-0134425-555-0177

345 Stewart StChatsworthCA91746

500000

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XLinq Creating XML via DOM (without XLinq)

XmlDocument doc = new XmlDocument();

XmlElement name = doc.CreateElement("name");name.InnerText = "Patrick Hines";XmlElement phone1 = doc.CreateElement("phone");phone1.SetAttribute("type", "home");phone1.InnerText = "206-555-0144";XmlElement phone2 = doc.CreateElement("phone");phone2.SetAttribute("type", "work");phone2.InnerText = "425-555-0145";XmlElement street1 = doc.CreateElement("street1");street1.InnerText = "123 Main St";XmlElement city = doc.CreateElement("city");city.InnerText = "Mercer Island";XmlElement state = doc.CreateElement("state");state.InnerText = "WA";XmlElement postal = doc.CreateElement("postal");postal.InnerText = "68042";XmlElement address = doc.CreateElement("address");address.AppendChild(street1);address.AppendChild(city);address.AppendChild(state);address.AppendChild(postal);XmlElement contact = doc.CreateElement("contact");contact.AppendChild(name);

contact.AppendChild(phone1);contact.AppendChild(phone2);contact.AppendChild(address);XmlElement contacts = doc.CreateElement("contacts");contacts.AppendChild(contact);doc.AppendChild(contacts);

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XLinq Creating XML via XLinq

Functional construction:

XElement contacts =

new XElement("contacts",new XElement("contact",

new XElement("name", "Patrick Hines"),new XElement("phone", "206-555-0144",

new XAttribute("type", "home")),new XElement("phone", "425-555-0145",

new XAttribute("type", "work")),

new XElement("address",new XElement("street1", "123 Main St"),new XElement("city", "Mercer Island"),new XElement("state", "WA"),new XElement("postal", "68042")

))

);

Imlicitly no XML document Can be added if some processing information is needed:

XDocument contactsDoc =new XDocument(

new XDeclaration("1.0", "UTF-8", "yes"),new XComment("XLinq Contacts XML Example"),new XProcessingInstruction("MyApp", "123-44-4444"),

new XElement("contacts",new XElement("contact",

new XElement("name", "Patrick Hines"),

Resulting XML:

Patrick Hines

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XLinq XML Namespaces

There is a support for XML namespaces, but namespace aliases are always expanded into full names

Creating element from a http://myCompany.com namespace:

XElement contacts = new XElement("{http://myCompany.com}contacts", );

Instead of explicit alias support, existing language facilities should be used. Typical pattern:

string myNs = "{http://mycompany.com}";

XElement contacts =new XElement(myNs+"contacts",

new XElement(myNs+"contact",new XElement(myNs+"name", "Patrick Hines"),new XElement(myNs+"phone", "206-555-0144",

new XAttribute("type", "home")),)

));

Results in following XML:

Patrick Hines206-555-0144

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XLinq Loading Existing XML Data

From string:

XElement contacts = XElement.Parse(@"

Patrick Hines206-555-0144425-555-0145

123 Main StMercer Island

WA68042

10

");

From file:

XElement contactsFromFile = XElement.Load(@"c:\myContactList.xml");

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XLinq Creating XElements

XElements constructor:

public XElement(XName name, params object[] contents)

Any of the parameters passed to contents can be:

1. A string, which is added as text content

2. An XElement, which is added as a child element

3. An XAttribute, which is added as an attribute

4. An XProcessingInstruction, XComment, orXCData, which is added as child content5. An IEnumerable, which is enumerated, and these rules are applied recursively

6. Anything else, ToString() is called and the result is added as text content

7. null, which is ignored

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XLinq Adding IEnumerables to XElement

class Person { public string Name; public string[] PhoneNumbers; }

var persons = new [] {new Person { Name="Patrick Hines",

PhoneNumbers = new string[] {"206-555-0144", "425-555-0145"} },

new Person { Name="Gretchen Rivas",PhoneNumbers = new string[] {"206-555-0163"} }

};

Following code using Standard Query Operators on IEnumerable can be used to transform a datastructureto XML:

XElement contacts =

new XElement("contacts",fromp in persons

select new XElement("contact",

new XElement("name", p.Name),

fromph in p.PhoneNumbers

select new XElement("phone", ph))

);

Console.WriteLine(contacts);

Output:

Patrick Hines206-555-0144425-555-0145

Gretchen Rivas206-555-0163

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XLing Element Text as Value (1)

XElement (text inside XElement) can be explicitly converted to a value:

XElement name = new XElement("name", "Patrick Hines");

string nameString = (string) name;

Console.WriteLine(nameString);

ToString() returns the XML representation of the whole element:

string nameString = name.ToString();Console.WriteLine(nameString);

Explicit type operators are provided for following types:string, bool, bool?, int, int?, uint, uint?, long, long?, ulong, ulong?, float,float?, double, double?, decimal, decimal?, DateTime, DateTime?, TimeSpan,TimeSpan?, GUID, GUID?

Output:

Patrick Hines

Output:

Patrick Hines

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XLing Element Text as Value (2)

All element text is merged together:

XElement xhtml = new XElement(body",

1234,

new XElement("br", null),

5678,

"some text",

new XElement("br", ""),

new XElement("em", "EMPHASED TEXT"),"other text\nwith newline"

);

Console.WriteLine(nameString);

Console.WriteLine((string) nameString);

Output:

1234
5678some text
EMPHASED TEXTother textwith newline

Output:

12345678some textEMPHASED TEXTother text

with newline

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XLinq Traversing XML

XML data:

Met in 2005.Patrick Hines206-555-0144425-555-0145

Code examples:

foreach (c in contact.Content()) {Console.WriteLine(c);

}

foreach (c in contact.Content()) {Console.WriteLine(c)

}

foreach (x in contact.Elements()) {Console.WriteLine(x);

}

foreach (x in contact.Elements("phone")) {Console.WriteLine(x);

}

XElement name = contact.Element("name");

string name = (string) contact.Element("name");

Met in 2005.Patrick Hines206-555-0144425-555-0145

Patrick Hines206-555-0144

425-555-0145

206-555-0144425-555-0145

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XLinq - Queries Example flattening contacts:

new XElement("contacts",from c in contacts.Elements("contact")select new object[] {

new XComment("contact"),new XElement("name", (string)c.Element("name")),c.Elements("phone"),new XElement("address", c.Element("address"))

});

Results in:

Patrick Hines206-555-0144425-555-0145

WA

Gretchen Rivas

WA

Scott MacDonald925-555-0134425-555-0177...

Patrick Hines

206-555-0144425-555-0145

12

Merce

WA

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XLinq Schema Aware programming

Without schema:

public static double GetTotalByZip(XElement root, int zip) {return (

from order in root.Elements("order"),item in order.Elements("item"),

where (int) order.Element("address").Element("postal") == zipselect ((double) price * (int) qty)

).Sum();

}

With schema (currently neither implemented nor specified probable XLinq extension in final version):

public static double GetTotalByZip(Orders root, int zip) {return (

from order in root.OrderCollection,item in order.Items

where order.Address.Postal == zipselect (item.Price * item.Quantity)

).Sum();

}

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XLinq in Visual Basic 9 (1)

Using C# 3.0 functional approach:

Dim contacts As XElement = _

New XElement("contacts", _New XElement("contact", _New XElement("name", "Patrick Hines"), _

New XElement("phone", "206-555-0144", _New XAttribute("type", "home")), _

New XElement("phone", "425-555-0145", _New XAttribute("type", "work")), _

New XElement("address", _New XElement("street1", "123 Main St"), _

New XElement("city", "Mercer Island"), _New XElement("state", "WA"), _

New XElement("postal", "98040"))))

Using XML literals:

Dim contacts As XElement = _

Patrick Hines

206-555-0144425-555-0145

123 Main St

Mercer IslandWA98040

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Pavel Jeek

XLinq in Visual Basic 9 (2)

Visual Basic expressions in XML literals:

Dim myName = "Patrick HinesDim contact As XElement =

Dim MyName = "Patrick HinesDim elementName = "contactDim contact As XElement =

Late bound XML:

For Each Dim phone In contact.phoneConsole.WriteLine(CStr(phone.@type))

NextConsole.WriteLine(CStr(contacts...city(0)))

For Each Dim phone In contact.Element("phone")Console.WriteLine(CStr(phone.Attribute("type")))

NextConsole.WriteLine(CStr(ElementAt(contact.Descendants("city"),0)))

csharp 3.0 and linq - 2007

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