What is new in .NET4.5 and VS2012

          ·         ASP.NET Core Runtime and Framework

·         Asynchronously Reading and Writing HTTP Requests and Responses

·         Improvements to HttpRequest handling

·         Asynchronously flushing a response

·         Support for await and Task-Based Asynchronous Modules and Handlers

·         Asynchronous HTTP modules

·         Asynchronous HTTP handlers

·         New ASP.NET Request Validation Features

·         Deferred ("lazy") request validation

·         Support for unvalidated requests

·         AntiXSS Library

·         Support for WebSockets Protocol

·         Bundling and Minification

·         Performance Improvements for Web Hosting

·         Key Performance Factors

·         Requirements for New Performance Features

·         Sharing Common Assemblies

·         Using multi-Core JIT compilation for faster startup

·         Tuning garbage collection to optimize for memory

·         Prefetching for web applications

·         ASP.NET Web Forms

·         Strongly Typed Data Controls

·         Model Binding

·         Selecting data

·         Value providers

·         Filtering by values from a control

·         HTML Encoded Data-Binding Expressions

·         Unobtrusive Validation

·         HTML5 Updates

·         ASP.NET MVC 4

·         ASP.NET Web Pages 2

·         Visual Studio 2012 Release Candidate

·         Project Sharing Between Visual Studio 2010 and Visual Studio 2012 Release Candidate (Project Compatibility)

·         Configuration Changes in ASP.NET 4.5 Website Templates

·         Native Support in IIS 7 for ASP.NET Routing

·         HTML Editor

·         Smart Tasks

·         WAI-ARIA support

·         New HTML5 snippets

·         Extract to user control

·         IntelliSense for code nuggets in attributes

·         Automatic renaming of matching tag when you rename an opening or closing tag

·         Event handler generation

·         Smart indent

·         Auto-reduce statement completion

·         JavaScript Editor

·         Code outlining

·         Brace matching

·         Go to Definition

·         ECMAScript5 support

·         DOM IntelliSense

·         VSDOC signature overloads

·         Implicit references

·         CSS Editor

·         Auto-reduce statement completion

·         Hierarchical indentation.

·         CSS hacks support

·         Vendor specific schemas (-moz-,-webkit)

·         Commenting and uncommenting support

·         Color picker

·         Snippets

·         Custom regions

·         Page Inspector

·         Publishing

·         Publish profiles

·         ASP.NET precompilation and merge

 

Source : http://www.asp.net/vnext/overview/whitepapers/whats-new

We will see each feature one by one in details.