Programming Visual Basic .NET, Second Edition

Chapter 17. Assemblies and Versioning

The basic unit of .NET programming is the assembly. An assembly is a collection of files that appears to the user to be a single dynamic link library (DLL) or executable (EXE). DLLs are collections of classes and methods that are linked into your running program only when they are needed.

Assemblies are the .NET unit of reuse, versioning, security, and deployment. This chapter discusses assemblies in detail, including the architecture and contents of assemblies, private assemblies, and shared assemblies.

In addition to the object code for the application, assemblies contain resources such as gif files, type definitions for each class you define, as well as metadata about the code and data.

PE Files

On disk, assemblies are Portable Executable (PE) files. PE files are not new. The format of a .NET PE file is exactly the same as a normal Windows PE file. PE files are implemented as DLLs or EXEs. Logically (as opposed to physically), assemblies consist of one or more modules. Note, however, that an assembly must have exactly one entry point—DLLMain, WinMain, or Main DLLMain is the entry point for DLLs, WinMain is the entry point for Windows applications, and Main is the entry point for DOS and Console applications.

Modules are created as DLLs and are the constituent pieces of assemblies. Standing alone, modules cannot be executed; they must be combined into assemblies to be useful.

You deploy and reuse the entire contents of an assembly as ...