If you want to learn to learn asp.net or are learning, I think you should take care of the follow namespaces:

 System
 System.Collections
 System.Web
 System.Data
 System.XML

ASP.NET makes heavy use of these namespaces; therefore, it is vital we understand their purpose!

The following are some key points about ASP.NET:
 ASP.NET is a key part of the wider Microsoft .NET initiative,
Microsoft’s new application development platform.
 .NET is both an application architecture to replace the Windows DNA
model and a set of tools, services, applications and servers based around
the .NET Framework and common language runtime (CLR).
 Rather than just being ASP 4 or an incremental upgrade,ASP.NET is a
complete rewrite from the ground up, using all the advanced features
.NET makes available.
 ASP.NET can take advantage of all that .NET has to offer, including
support for around 20 or more .NET languages from C# to Perl.NET,
and the full set of .NET Framework software libraries.

 Web applications written in ASP.NET are fast, efficient, manageable,
scalable, and flexible, but, above all, easy to understand and to code!
 Components and Web applications are all compiled .NET objects
written in the same languages, and they offer the same functionality, so
no need to leave the ASP environment for purely functional reasons.
 You’ll have less need for third-party components.With a few lines of
code,ASP.NET can talk to XML, serve as or consume a Web service,
upload files, “screen scrape” a remote site, or generate an image.