.NET Framework 3.5

C# v3.0 - Visual Studio 2008

Query Expressions

Make frequent use of anonymous types

Expression Trees

These represent code in a tree-like data structure where each node is an expression (for example a method call or a binary operation).
You can instruct the compiler to create an expression tree for you based on an anonymous lambda expression.
You can also create expression trees manually using the System.Linq.Expressions namespace.

.NET Framework 3.5

VSTO - Office Interop API Extensions

System.Collections.Generic.HashSet

Implicitly Typed Variables - var

Auto Implemented Properties

Anonymous Types

Generic Delegates - System.Func/Action/Predicate

Object Initializers

Partial Methods

Collection Initializers

Extension Methods

Lamda Expressions

Language Intergrated Query (LINQ)

Query Expressions

Expression Trees