What does an Assembly contain?

An assembly is the core building block of .Net, assemblies are self-contained, they contain all the information required to process the assembly. Any .Net assembly contains the following details.

1. The MSIL code of the assembly
2. Assembly Manifest
3. Type Metadata
4. Resources

Now let us see these in detail.

MSIL Code
The Assembly code written in any of the .Net Languages C#, VB.Net etc are compiled into an Intermediate Language called MSIL (Microsoft Intermediate Language) code. This MSIL code is stored within the assembly, this forms the core part of the assembly, the MSIL code of the assembly contains the compiled version of all the classes and code written for that assembly.

Assembly Manifest
The Assembly Manifest contains the following information.
Name, Version, Culture details of the assembly.
Security information relating to the assembly.
List of files in the assembly and their relationship.
External dependencies/references of the assembly.

Type Metadata
Type Metadata of an Assembly contains the details of various types (classes and class members) which are stored in the compiled MSIL code. This data is used to describe the content of the assembly types to the external applications / assemblies.

Resources
Resources are external files like image file, sound clips etc which are referenced from the assembly code, these dependent files are also packed as part of the assembly so as to make it a single piece of executable file or Library.