DLL Vs WebService

DLL :

• A dll (dynamically linked library) is a small piece of code to be shared by one or more application, it is specific to Microsoft.
• Linux cannot link and use a DLL prepared in windows(say asp.net).
• Linux uses a very similar callstruct called a shared object (.so) it is compiled using a c compiler (typically gcc) and linked using a linker.
  

A Web Service :

• A web service is typically an application programming interface(API) or Web API that is accessed via HTTP and executed on a remote system, hosting the requested service.
• So, it is platform independent in the sense an application on Linux platform can request and use a web service via HTTP.