New features of asp.net 4.5 vs 4.0 framework

1. Asynchronously Reading and Writing HTTP Requests and Responses while in asp.net 4.0 it happens synchronously.
ASP.NET 4 introduced the ability to read an HTTP request entity as a stream using the HttpRequest.GetBufferlessInputStream method. This method provided streaming access to the request entity. However, it executed synchronously, which tied up a thread for the duration of a
request.ASP.NET 4.5 supports the ability to read streams asynchronously on an HTTP request entity, and the ability to flush asynchronously. ASP.NET 4.5 also gives you the ability to double-buffer an HTTP request entity, which provides easier integration with downstream HTTP handlers such as .aspx page handlers and ASP.NET MVC controllers.

2.Support for await and Task-Based Asynchronous Modules and Handlers
The .NET Framework 4 introduced an asynchronous programming concept referred to as a task. Tasks are represented by the Task type and related types in the System.Threading.Tasks namespace. The .NET Framework 4.5 builds on this with compiler enhancements that make working with Task objects simple. In the .NET Framework 4.5, the compilers support two new keywords: await and async.

3.Support for WebSockets Protocol
WebSockets protocol is a standards-based network protocol that defines how to establish secure, real-time bidirectional communications between a client and a server over HTTP. Microsoft has worked with both the IETF and W3C standards bodies to help define the protocol. The WebSockets
protocol is supported by any client (not just browsers), with Microsoft investing substantial resources supporting WebSockets protocol on both client and mobile operating systems.WebSockets protocol makes it much easier to create long-running data transfers between a client and a server. For example, writing a chat application is much easier because you can establish a true long-running connection between a client and a server.

4.Bundling and Minification
Bundling lets you combine individual JavaScript and CSS files into a bundle that can be treated like a single file. Minification condenses JavaScript and CSS files by removing whitespace and other characters that are not required. These features work with Web Forms, ASP.NET MVC, and Web Pages.

5.Performance Improvements for Web Hosting
The .NET Framework 4.5 and Windows 8 introduce features that can help you achieve a significant
performance boost for web-server workloads. This includes a reduction (up to 35%) in both startup time and in the memory footprint of web hosting sites that use ASP.NET.

6.Unobtrusive Validation
You can now configure the built-in validator controls to use unobtrusive JavaScript for client-side validation logic. This significantly reduces the amount of JavaScript rendered inline in the page markup and reduces the overall page size.

7.Provides HTML editor, Javascript Editor and CSS editor with smart and intelligent features.