C# 3.5 Features

1. .Net 3.5
-Prabhakaran

2. .Net 3.5 Framework

3. What is new in 3.5 C#?
 Implicitly Typed Local Variables
 Automatic Properties
 Object Initializer
 Collection Initializers
 Extension Methods
 Lambda Expressions
 Query Syntax
 Anonymous Types
 Expression Trees

4. 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<int,Order>();
Are equivalent to:
int i = 5;
string s = "Hello";
double d = 1.0;
int[] numbers = new int[] {1, 2, 3};
Dictionary<int,Order> orders = new
Dictionary<int,Order>();
Errors:
var x; // Error, no initializer to infer type from
var y = {1, 2, 3}; // Error, collection initializer not
permitted
var z = null; // Error, null type not permitted

5. Automatic Properties
 public class Person {
private string _firstName;
private string _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; } } }

6.  For example, using automatic properties I can now re-write the code
above to just be:
 public class Person {
public string FirstName {
get; set;
}
public string LastName {
get; set;
}
public int Age {
get; set;
}
}
 Or If I want to be really terse, I can collapse the whitespace even further
like so:
 public class Person {
public string FirstName { get; set; }
public string LastName { get; set; }
public int Age { get; set; }
}

7. Object Initializer
Person person = new Person();
person.FirstName = "Scott";
person.LastName = "Guthrie";
person.Age = 32;
3.5
Person person = new Person { FirstName="Scott", Last
Name="Guthrie", Age=32 };
Person person = new Person {
FirstName = "Scott",
LastName = "Guthrie"
Age = 32,
Address = new Address {
Street = "One Microsoft Way",
City = "Redmond",
State = "WA",
Zip = 98052
}
};

8. Collection Initializers
List<Person> people = new List<Person>();
people.Add( new Person { FirstName = "Scott", LastName = "Guthrie", A
ge = 32 } );
people.Add( new Person { FirstName = "Bill", LastName = "Gates", Age
= 50 } );
people.Add( new Person { FirstName = "Susanne", LastName = "Guthrie
", Age = 32 } );
3.5
List<Person> people = new List<Person> {
new Person { FirstName = "Scott", LastName = "Guthrie", Age = 32 },
new Person { FirstName = "Bill", LastName = "Gates", Age = 50 },
new Person { FirstName = "Susanne", LastName = "Guthrie", Age = 3
2}
};

9. Extension Methods
Extension methods allow developers to add new methods to the public contract of an
existing CLR type, without having to sub-class it or recompile the original type.
Example:
string email = Request.QueryString["email"];
if ( EmailValidator.IsValid(email) ) {
}
3.5
string email = Request.QueryString["email"];
if ( email.IsValidEmailAddress() ) {
}
public static class ScottGuExtensions
{
public static bool IsValidEmailAddress(this string s)
{
Regex regex = new Regex(@"^[w-.]+@([w-]+.)+[w-]{2,4}$");
return regex.IsMatch(s);
}
}

11. Lambda Expressions

12. Query Syntax
 Query syntax is a convenient declarative shorthand for expressing queries
using the standard LINQ query operators.

13. Anonymous Types