in windows invironment,the file system is splited into directories
and files.files holds the actual data,but directories are
storage for logical listing of files in the system.to deal with
files and folders(directories),CLR uses System.IO namespace.
the classes used are File,FileInfo,DirectoryInfo,Directory.

using SMO classes one can backup a sql server database
in .bak extension.It's a programming approach to backup
database.there are other ways but using SMO classes it
is efficient and error free.

you will need to access html elements from asp.net
code behind file.i show you how to access widely used
html textarea element from code behind file -

you may read many article in web about how to make a page
not to be cached using meta tags like that in the head
section -

It's a good idea to identify the errors at run time to detect
and handle it. .Net framework has built in mechanism for that.
these exceptions occurs because of user,logic and system errors.

The abstract class indicates that a class may be used
as a base class for other classes and is not instantiable.