What is An Assemblies in c# .net?

In .NET assemblies can be broadly classified into 2 types

Weak Named Assemblies
Strong Named Assemblies

An assembly name consists of 4 Parts

Simple textual name.
Version number.
Culture information (otherwise the assembly is language neutral)
Public key token

We use AssemblyVersion attribute to specify the Assembly version. The default is 1.0.0.0. The version number of an assembly consists of the following 4 parts:

Major Version
Minor Version
Build Number
Revision Number

Strong naming an assembly :

Strong naming an assembly AssemblyCulture attribute is used for specifying the culture. By default, an assembly is language neutral. If you specify any string other than an empty string for the culture parameter, the assembly becomes a satellite assembly. In fact, compilers use this attribute to distinguish between main assembly (language neutral) and a satellite assembly.

To generate the key pair, use strong naming tool

sn.exe-kc:\KeyPairFile.sk

To strong name an assembly

[assembly: AssemblyKeyFile("KeyPairFile.snk")]

A strongly named assembly should have all of the following

The textual assembly name.
The assembly Version number.
The assembly should have been signed with private / publickey pair.

Weak naming an assembly :

If the assembly is not signed with private/public key pair, the assembly is weak named and not guaranteed to be unique, and may cause DLL hell.

Strong named assemblies are guaranteed to be unique and solves DLL hell. You cannot install an assembly into GAC unless, the assembly is strongly named.