Assembly in Microsoft .Net is a logical unit of code which contains the code adn run by Common Language Runtime (CLR). It is the smallest unit of deployment of a .net application and it can be a .dll or an exe. Assembly is really a collection of types and resource information that are built to work together and form a logical unit of functionality. Assembly executable application files that you can run directly from Windows without the need for any other programs (.exe files), and libraries (.dll files) for use by other applications. Assembly blocks of .NET Framework applications.