Assembly Versioning

Assembly version details are stored in a file called AssemblyInfo, this file gets automatically created when you create a new project in Visual Studio, the version information of the assembly is specified in this file.

A .Net Assembly version is a four part name, and contains the following 

Major Version
Minor Version
Build Version
Release Version.

The four parts of the Assembly version are organized as follows.
<Major Version>.<Minor Version>.<Build Version>.<Release Version>

When there are multiple Assemblies using in a bigger project/application, it is advisable to use the same version number for all the assemblies used in the project, this way we need not keep track of the individual assembly versions along with the Application version.

The assembly version is specified in the AssemblyInfo file as follows.
[assembly:AssemblyVersionAttribute("4.3.2.1")]

The AssemblyInfo file also contains additional information on the assembly like culture, for shared assemblies the file also contains a mapping to the key file used to sign the assembly. The file also contains attributes the details of the assembly owner like Name, Copyright, Trademark etc.