What’s New in C# 3.0
Language Integrated Query(LINQ)
- LINQ enables queries to be written in C# program to query both local collections
(such as lists or XML documents) or remote data sources (such as a database)
Implicitly typed local variables
- let you omit the variable type in a declaration statement, allowing the compiler to infer it
Object initializers
- simplify object construction by allowing properties to be set inline after the constructor call
Lambda expressions
- miniature functions created by the compiler on the fly, and are particularly useful in “fluent” LINQ queries
Extension methods
- extend an existing type with new methods, making static methods feel like instance methods
Query expressions
- provide a higher-level syntax for writing LINQ queries that can be substantially simpler when working
with multiple sequences or range
variables
Expression trees
- miniature code DOMs that describe lambda expressions assigned to the
special type Expression<TDelegate>
Expression trees make it possible for LINQ queries to execute remotely
Automatic properties
- cut the work in writing properties that simply get/set a private backing field by having the compiler do that work automatically
Partial methods
- let an auto-generated partial class provide customizable hooks for manual authoring which “melt away” if unused
What’s New in C# 4.0
Dynamic binding
- defers binding
Optional parameters
- allow functions to specify default parameter values so that callers can omit arguments and named arguments
allow a function caller to identify an argument by name rather than position
Type variance rules
- type parameters in generic interfaces and generic delegates can be marked as covariant or
contravariant, allowing more natural type conversions
COM interoperability
What’s New in C# 5.0
C# 5.0’s big new feature is support for asynchronous functions via two new
keywords, async and await. Asynchronous functions enable asynchronous continuations,
which make it easier to write responsive and thread-safe rich-client applications.
They also make it easy to write highly concurrent and efficient I/O-bound
applications that don’t tie up a thread resource per operation