It depends on functionality and requirement of the component. e.g If you are going to implement interfaces of a component which is no more supported in current technology that is Interfaces are uncompilable with current technologies than you have to make some wrapper class which 'Understands' those interfaces and translate into native interfaces which are supported by the current technology. e.g Wrapper or Adapter Pattern has been used for creating Wrapper classes for use of Microsoft COM Legacy Components into .Net environment. as CLR understands/executes only manage code which is said MSIL , .net framework alternatively creates Wrapper classes(Adapter pattern). There are other many Patterns e.g Iterator pattern which is implemented in XPathiterator class.

i want guidance from you i am asp.net developer want to know that which .net design pattern or  application block released by microsoft is best for asp.net web develpment like for shopping portals or any type of site

thanks