1). Web.config Refactoring. As major configuration elements have been moved to the machine.config file, this allows the Web.config file in ASP.NET 4 applications to be empty or to specify only which version of the framework the application is targeting, as shown at our blog.
2). Extensible Output Caching.
In Asp.Net output caching has enabled developers to store the generated output of pages, controls, and HTTP responses in memory.On servers that experience heavy traffic, the memory requirements for output caching can compete with memory requirements for other parts of a Web application.
ASP.NET 4 adds extensibility to output caching that enables you to configure one or more custom output-cache providers which lets you design more aggressive and more intelligent output-caching strategies for Web sites. The easiest way to choose a different output-cache provider for different Web user controls is to do so declaratively by using the new providerName attribute in a page or control directive, as shown at our blog.
3). Auto-Start Web Applications. Some
Web applications must load large amounts of data or must perform expensive initialization processing before serving the first request. This was done in earlier version by implementing certain code in GLOBAL.asax file but however it was not successful in every possible situation. To handle this schenario new auto-start feature is available when ASP.NET 4 runs on IIS 7.5 on Windows Server 2008 R2.
4). Permanent Page Redirection. Many a times there are scnerios of website and content upgradation and we may change even pages or add pages. But search engine might retain previous links which may cause "Page not found" issue. This can be solved by using RedirectPermanent helper method in ASP.Net4 as at our blog. Search engines and other user agents that recognize permanent redirects will store the new URL that is associated with the content, which eliminates the unnecessary round trip made by the browser for temporary redirects.
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