The Pre-Requisites

It should be noted that ASP.NET 4.0 ships with Visual Studio 2010. To work with ASP.NET 4.0, you should have Visual Studio 2010 installed in your system. As of this writing, Visual Studio 2010 Beta 2 has been released. You can download a copy of Visual Studio 2010 Beta 2 from this link: http://msdn.microsoft.com/en-us/vstudio/dd582936.aspx

So, what’s new?

The new features and enhancements in ASP.NET 4.0 include:

State Management Improvements – These include improvements to ViewState, Session and Cache
Enhancements to ASP.NET Data Presentation Controls
Enhanced Support for Performance Monitoring
Enhanced control over ControlIDs of Controls
Support for Routing
Search Engine Optimization Enhancements
Simplification of Web.Config file

State Management Improvements

In ASP.NET 4.0, there has been marked improvements in Cache, Session and ViewState. The ASP.NET 4.0 Cache API now allows you to store data in any of the following cache storages:

Disk-based output caches – This is used to store cache data in disk
Custom object caches – This is used to store cache data using custom cache providers
Distributed object caches – This is used to store cache data in a separate server
Cloud-based object caches – This is used to store cache data in cloud databases

Now you can use ASP.NET 4.0 Cache API to design and implement your custom cache storage provider too. You can also configure your custom cache provider easily in your application's web.config file. Here's an example:

type="MyDiskCacheProvider.OutputCacheEx.DiskOutputCacheProvider,MyDiskCacheProvider"/>

There has also been a marked improvement in ViewState in ASP.NET 4.0. You can now use the ViewStateMode property - a new property introduced for all controls in ASP.NET 4.0, to determine whether or not ViewState should be enabled for a particular control in your webform. This gives your better control and flexibility on the ViewState as the EnableViewState property introduced in the earlier versions of ASP.NET resulted in inconsistent behavior of the ViewState.