Vs 2008 and .Net Framework 3.5 has many new features and improvements prior versions.
The following are some of the features:
1. VS 2008 Multi-Targeting Support
VS 2008 support multiple versions .net framework i.e 2.0, 3.0, 3.5. Where VS 2002 supports only .Net 1.0, VS 2003 supports 1.1, and VS 2005 supports 2.0 . That means you can open an existing project or create a new one with VS 2008, you can pick which version of the .NET Framework to work with - and the IDE will update its compilers and feature-set to match this. And that features, controls, projects, item-templates, and assembly references that not work with that version of the framework will be hidden. Unfotunately it does not support .net1.0 and .net 1.1. but we can run VS 2008 side by side with VS 2005 , VS 2003 and VS 2002 on the same machine.
Now, you can stop putting alerts in your code unnecessarly to check the values of the variable or flow of control. Instead of alert boxes , now you can keep break points to look the values of the variables at client script within your server-side .aspx and .master source files. Its like putting break points in server script.
4. Support of AJAX
5. Split of Design view and Source view Editing
In VS 2005 and previous versions , we have design view , source view .Besides this features it supports a new "split-view" mode when working on pages. This allows you to see both the HTML source and the Design View at the same-time, and easily have any changes you make in one view be updated in the other. We can set the split view as horizontal as well as vertical to use maximum screen.
6. CSS Manager
VS 2008 supports a new tool window inside the IDE called "Manage Styles". This shows all of the CSS stylesheets, and their corresponding rules, for the page you are currently editing. It can be used both when you are in design-view, as well as when you are in source view on a page.
7. Nested Master Pages
The great feature in asp.net 2.0 is Master page. By including master page we can avoid redundant code like header , footer and menus which contains in all pages. Now in VS 2008,we can create nested master pages.
8. List View Control
One of the new controls in ASP.NET 3.5 is the control. The ListView control supports the data editing, insertion, deleting, paging and sorting semantics of higher-level controls like the GridView. But - unlike the GridView - it provides you with complete control over the html markup generated.