An assembly in the .NET Framework is a collection of types and resources that are built to work together and form a logical unit of functionality. Assemblies take the form of executable (.exe) or dynamic link library (.dll) files, and are the building blocks of .NET applications.

Assemblies provide the following benefits:

• Reusability: Assemblies can be reused in multiple applications.
• Versioning: Assemblies can be versioned to allow multiple versions of an assembly to be used in the same application.
• Security: Assemblies can be signed to verify their authenticity and to control who can use them.

Assemblies are composed of the following parts:

• Manifest: The manifest is a file that contains information about the assembly, such as its name, version, and dependencies.
• Types: Assemblies can contain types, such as classes, interfaces, and delegates.
• Resources: Assemblies can contain resources, such as images, strings, and binary data.

When an assembly is loaded, the .NET Framework uses the manifest to locate the types and resources in the assembly. The .NET Framework then creates instances of the types and executes the code in the assembly.

Assemblies are an important part of the .NET Framework. They provide a way to organize and manage code, and they make it easy to reuse code in multiple applications.

Assemblies can be defined as the basic building blocks of .Net framework applications. Assemblies may or may not be executable that is they can be in the form of executable (.exe), or dynamic link library (.dll) file. It contains information about the version type, Meta data and manifest. Assembly is a collection of types and resource information that are built work together to form a functionality. It consist of single or multiple files. Multiple files include one modules which contains manifest while others assemblies exists as non-manifest modules.

.Net supports three types of assemblies

Private assembly

Private assembly can be used in single application where this assembly can be stored in application’s directory. Also we can say that private assembly requires to copy in all application folder where we want to use assembly’s functionalities, without copying we cannot access private assembly’s features and power.

Public / shared assembly

Public or shared assembly used by multiple application, if more than one application use assembly than that assembly must be add or copy to single location known as Global Assembly Cache (GAC). For calling assemblies within same application the same copy of shared assembly is used from original location. Shared assembly contains four part name including face name, version, public key token and cultural information. Public key token and version information makes impossible for two different assembly with same name or same assembly with different version to mix with each other.

Satellite assembly

Satellite assembly used by deploying languages and cultural specific resources for application. It contains static objects like images and other non-executable files used by the application.