Assembly in .Net

For the counterpart to assembly language in the Microsoft .NET framework, see Common Intermediate Language.

In the Microsoft .NET framework an assembly is a partially compiled code library for use in deployment, versioning and security. In the Microsoft Windows implementation of .NET, an assembly is a PE (portable executable) file. There are two types, process assemblies (EXE) and library assemblies (DLL).

This means that a library may have either .dll or .exe as its extension.

The code in an assembly is compiled into MSIL, which is then compiled into machine language at runtime by the CLR.

An assembly can consist of one or more files. Code files are called modules. An assembly can contain more than one code module and since it is possible to use different languages to create code modules this means that it is technically possible to use several different languages to create an assembly.

The name of an assembly consists of four parts:

1. The short name. On Windows this is the name of the PE file without the extension.
2. The culture. This is an RFC 1766 identifier of the locale for the assembly. In general, library and process assemblies should be culture neutral; the culture should only be used for satellite assemblies.
3. The version. This is a dotted number made up for 4 values — major, minor, build and revision. The version is only used if the assembly has a strong name (see below).
4. A public key token. This is a 64-bit hash of the public key which corresponds to the private key used to sign^[1] the assembly. A signed assembly is said to have a strong name.